Replacing synchronized blocks with ReentrantLocks in core part of SDK

[Myllyenko]

Continuation of https://github.com/ydb-platform/ydb-java-sdk/pull/338

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 6 lines in your changes missing coverage. Please review.

Project coverage is 47.21%. Comparing base (9a7adfa) to head (863193b).

Files with missing lines	Patch %	Lines
...src/main/java/tech/ydb/core/impl/YdbDiscovery.java	70.58%	4 Missing and 1 partial :warning:
...a/tech/ydb/core/impl/call/ReadWriteStreamCall.java	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #341 +/- ## ============================================ + Coverage 47.19% 47.21% +0.01% Complexity 1750 1750 ============================================ Files 311 311 Lines 12499 12499 Branches 1238 1238 ============================================ + Hits 5899 5901 +2 + Misses 6140 6138 -2 Partials 460 460 ```

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[alex268]

I am not sure that we have to remove synchronized from call classes. They are just simple wrappers on GrpcCall and all their calls are not blocking. In this case, synchronized just adds thread safety to GrpcCall, especially with case data race on start() and cancel(). Replacing them by ReentrantLock makes them more complex and may reduce a performance

[Myllyenko]

I am not sure that we have to remove synchronized from call classes. They are just simple wrappers on GrpcCall and all their calls are not blocking. In this case, synchronized just adds thread safety to GrpcCall, especially with case data race on start() and cancel(). Replacing them by ReentrantLock makes them more complex and may reduce a performance

Reverted changes in StreamCalls.