Shared metadata cache

[AlexPeshkoff]

Since FB3 we use per-attachment metadata cache in SS. This slows attach to already opened DB, makes a lot of other caches not enough efficient and causes serious loss of RAM for DBs with big metadata.

[vpavlov33]

When to expect this to arrive in main tree? I would like to test it when merged.

[AlexPeshkoff]

Beginning of next year

[aafemt]

@AlexPeshkoff Why don't you just open PR from your working branch and let them to test CI artifacts?