Summary:
* Make new format_version=7 a supported setting.
* Fix a bug in compressed_secondary_cache.cc that is newly exercised by custom compression types and showing up in crash test with tiered secondary cache
* Small change to handling of disabled compression in fv=7: use empty compression manager compatibility name.
* Get rid of GetDefaultBuiltinCompressionManager() in public API because it could cause unexpected+unsafe schema change on a user's CompressionManager if built upon the default built-in manager and we add a new built-in schema. Now must be referenced by explicit compression schema version in the public API. (That notion was already exposed in compressed secondary cache API, for better or worse.)
* Improve some error messages for compression misconfiguration
* Improve testing with ObjectLibrary and CompressionManagers
* Improve testing of compression_name table property in BlockBasedTableTest.BlockBasedTableProperties2
* Improve some comments
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13713
Test Plan: existing and updated tests. Notably, the crash test has already been running with (unpublished) format_version=7
Reviewed By: mszeszko-meta, hx235
Differential Revision: D77035482
Pulled By: pdillinger
fbshipit-source-id: 95278de8734a79706a22361bff2184b1edb230ca
78c83ac1ec