DRIVERS-2862: Benchmark Collection and Client BulkWrite

[adelinowona]

The PR adds benchmarks for Collection::BulkWrite and Client::BulkWrite with insert-only operations and mixed operations. We already have a Small doc Bulk Insert and Large doc Bulk Insert benchmark in the benchmarking spec which may be sufficient for benchmarking Collection::BulkWrite with insert-only operations. However, the Small doc Bulk Insert and Large doc Bulk Insert benchmarks are implemented using insertMany and not all the drivers use Collection::BulkWrite in their implementation of insertMany. With that in mind, I have added explicit Collection::BulkWrite benchmarks to be implemented by all drivers who implement Collection::BulkWrite. This ensures we still maintain comprehensive performance testing for our batch-write performance.

Here are results of the new benchmarks as implemented on the C# driver:

Name	MB/sec
SmallDocClientBulkWriteMixedOps	1.8424719941
SmallDocCollectionBulkWriteMixedOps	0.7477088677
LargeDocClientBulkWriteInsert	94.242845107
LargeDocCollectionBulkWriteInsert	96.493395532
LargeDocBulkInsert	96.5527236825
SmallDocClientBulkWriteInsert	36.6208512962
SmallDocCollectionBulkWriteInsert	41.0499232896
SmallDocBulkInsert	42.1881191706

Please complete the following before merging:

• Update changelog.
• Test changes in at least one language driver.
• Test these changes against all server versions and topologies (including standalone, replica set, sharded
  clusters, and serverless).

[BorisDog]

partial review

[BorisDog]

There is some inconsistency in specifying the following action "Make X copies, DO NOT add _id", it's part of Setup step for bulk insert and part of Do task in other places. Should this be part of same step everywhere?

[BorisDog]

I think we need more details here: ordering and explicit count for each operation kind.