YT-26695: Introduce logical version to Hydra

Introduced a distinction between logical and physical versions of Hydra.

First, let's clarify what I mean when I write "physical mutation" and "logical mutation".
Physical mutation is an entry in the changelog.
Logical mutation is what people usually call "a mutation", a handler to a specific protobuf message, that changes the persistent state of Hydra.

Several unrelated logical mutations can be batched in one physical mutation. This may cause problems, since the version of the mutation is taken from the physical mutation. It lead to a few bugs, when people assumed that different logical mutations always have different mutation versions associated with them.
To combat that, a clear distinction between the two has been introduced in this PR.
commit_hash:1ac7c6a21601191f252c8cfcb8fd8bdbbe479d19

0 files changed, 0 insertions, 0 deletions