feat(bigquery): Support collation feature

[aandreassa]

Features:

• Added collation to Schema & Schema::Field
• Added default_collation to Table
• Added default_collation to Dataset
• Added unit tests & integration tests

Java reference: https://github.com/googleapis/java-bigquery/pull/2490/files
NodeJS reference: https://github.com/googleapis/nodejs-bigquery/pull/1188/files

b/266066248

[viacheslav-rostovtsev]

please add an integration test for field collation. Can be similar to "updates the table schema with default values"

[viacheslav-rostovtsev]

~

[aandreassa]

Thank you, updated it! I am creating a table since a field's collation is immutable after it.

Google::Cloud::Bigquery::Table::bigquery#test_0048_updates the table schema with collation:
  Google::Cloud::InvalidArgumentError: INVALID_ARGUMENT: Provided Schema does not match Table <table-name-redacted>.table_collation_test.
   Invalid schema update. Updating field collation is not supported. Field name has changed collation from "" to "und:ci"