feat: support RPC priority

[olavloite]

Adds support for setting RPC priority.

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/BeginTransactionRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/BeginTransactionRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/CommitRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/CommitRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteBatchDmlRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteBatchDmlRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteSqlRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteSqlRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ReadRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ReadRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/SpannerProto.java
• proto-google-cloud-spanner-v1/src/main/proto/google/spanner/v1/spanner.proto

[olavloite]

@thiagotnunes The implementation of this feature should be synchronized with #576 (Tagging), as they both set RequestOptions for both individual statements as well as transactions. The most important question regarding this is whether we want to use TransactionOption to pass in the options for a read/write transaction, or whether we want to add a withSomeOption on TransactionContext for the different options.

[codecov]

Codecov Report

Merging #676 (3abfd4e) into master (a2e5803) will increase coverage by 0.06%.
The diff coverage is 100.00%.

❗ Current head 3abfd4e differs from pull request most recent head 7abb3f8. Consider uploading reports for the commit 7abb3f8 to get more accurate results

@@             Coverage Diff              @@
##             master     #676      +/-   ##
============================================
+ Coverage     85.10%   85.17%   +0.06%     
- Complexity     2623     2633      +10     
============================================
  Files           155      154       -1     
  Lines         14374    14363      -11     
  Branches       1340     1342       +2     
============================================
  Hits          12233    12233              
+ Misses         1573     1565       -8     
+ Partials        568      565       -3     

Impacted Files	Coverage Δ	Complexity Δ
.../com/google/cloud/spanner/AbstractReadContext.java	86.82% <100.00%> (+0.28%)	44.00 <2.00> (+2.00)
...rc/main/java/com/google/cloud/spanner/Options.java	92.25% <100.00%> (+4.10%)	85.00 <5.00> (+11.00)
...oogle/cloud/spanner/PartitionedDmlTransaction.java	82.60% <100.00%> (+0.58%)	15.00 <0.00> (+1.00)
...ain/java/com/google/cloud/spanner/SessionImpl.java	86.90% <100.00%> (+0.23%)	31.00 <0.00> (+1.00)
...om/google/cloud/spanner/TransactionRunnerImpl.java	86.24% <100.00%> (+0.17%)	10.00 <0.00> (ø)
...a/com/google/cloud/spanner/SpannerRetryHelper.java	80.95% <0.00%> (-3.67%)	3.00% <0.00%> (ø%)
...m/google/cloud/spanner/connection/SpannerPool.java	87.36% <0.00%> (-0.53%)	33.00% <0.00%> (ø%)
...le/cloud/spanner/connection/ConnectionOptions.java	90.53% <0.00%> (-0.49%)	89.00% <0.00%> (-1.00%)
...ain/java/com/google/cloud/spanner/SessionPool.java	88.93% <0.00%> (ø)	72.00% <0.00%> (+1.00%)
...spanner/admin/database/v1/DatabaseAdminClient.java	87.96% <0.00%> (ø)	72.00% <0.00%> (ø%)
... and 3 more

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[elharo]

This change will break customers and requires a major version bump. This is not optional.

[olavloite]

This is no longer a breaking change, as the breaking changes that were needed for this and other changes were grouped into a separate change to avoid having to bump the version multiple times. That change added Options... options varargs to the methods that need to support a variety of query / update / transaction options.

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/BeginTransactionRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/BeginTransactionRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/CommitRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/CommitRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/CommitResponse.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteBatchDmlRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteBatchDmlRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteSqlRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ExecuteSqlRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ReadRequest.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/ReadRequestOrBuilder.java
• proto-google-cloud-spanner-v1/src/main/java/com/google/spanner/v1/SpannerProto.java
• proto-google-cloud-spanner-v1/src/main/proto/google/spanner/v1/spanner.proto

[olavloite]

@elharo Would you mind taking another look at this PR? As your review requested changes, this PR is currently blocked from merging.

(FYI: The samples build error is unrelated to this change)