Use a better ReliableStorageLock based on If-Match S3 atomic operations

[IvoDD]

Is your feature request related to a problem? Please describe.
The current ReliableStorageLock was being implemented before If-Match on put objects was announced by aws and hence uses a more complex structure than it is needed. This ticket lists all minor things we need to address when doing this simplification.

This is blocked on aws-sdk-cpp not having 1.11.455 or later which has the new If-Match on put requests support.

Describe the solution you'd like

• Use lock which just relies on a single ref key which gets overriden with If-Match statements.
• Think about how existing uses of the lock can upgrade to the new locking
• Rework C++ ReliableStorageLock tests to use a MockS3Client instead of the InMemoryStore. more info
• Make the storage lock configure the underlying storage with a MaxTimeoutPoliocy. more info
• Use Last-Modified time from S3 for expiration instead of the process time. more info
• Move slower cpp stress tests to a separate target. more_info

[IvoDD]

Also we need to think about:

• Dynamically detecting whether storage supports atomic operations
• Provide a means to fallback to the old storage lock (which will need some new APIs e.g. extending a lock)

[IvoDD]

Rework C++ ReliableStorageLock tests to use a MockS3Client instead of the InMemoryStore. #2014 (comment)

Attempting to write such python tests turned out futile because of the GIL handling. It would probably still be better to have the C++ tests use MockS3Client instead of InMemoryStore