feature: Add bulk inserts for sqlite

[glennawatson]

This fixes #470 and fixes #451

Change the SQL raw class to support IObjectBulkBlobCache interface. Implement the bulk insertions.

[codecov]

Codecov Report

Merging #499 into master will increase coverage by 0.15%.
The diff coverage is 70.11%.

@@            Coverage Diff             @@
##           master     #499      +/-   ##
==========================================
+ Coverage   54.61%   54.77%   +0.15%     
==========================================
  Files          57       57              
  Lines        3444     3531      +87     
  Branches      540      557      +17     
==========================================
+ Hits         1881     1934      +53     
- Misses       1400     1415      +15     
- Partials      163      182      +19

Impacted Files	Coverage Δ
....Sqlite3/SqlLiteCache/SqlRawPersistentBlobCache.cs	77.58% <70.11%> (-2.5%)	⬇️
...kavache.Sqlite3/Queues/OperationQueueCoalescing.cs	89.35% <0%> (-3.05%)	⬇️
src/Akavache.Sqlite3/Queues/OperationQueue.cs	87.67% <0%> (-2.3%)	⬇️
src/Akavache.Core/BlobCache/InMemoryBlobCache.cs	59.19% <0%> (+1.72%)	⬆️
src/Akavache.Core/BulkOperationsMixin.cs	78.94% <0%> (+8.77%)	⬆️

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