replication.synchro_queue_max_size configuration option

[maryiaLichko]

Resolves #4575.

Configuration reference: https://docs.d.tarantool.io/en/doc/gh-4575-rep-queue-max-size/reference/configuration/configuration_reference/#confval-replication.synchro_queue_max_size

Deployment: https://docs.d.tarantool.io/en/doc/gh-4575-rep-queue-max-size/reference/configuration/configuration_reference/#confval-replication.synchro_queue_max_size

[maryiaLichko]

@p7nov hey! please take a look

[p7nov]

There is a bit of a mess with commits and changes. Please fix it leaving only the related changes.
Also, some comments on the description itself from my side.

[p7nov]

Changes from another PR. Please separate the changes related to the current task only.

[Astronomax]

In essence, everything is correct. I think it's useful to also say: "The size limit isn't strict, i.e. if there's at least one free byte, the whole write request fits and no blocking is involved."

[maryiaLichko]

There is a bit of a mess with commits and changes. Please fix it leaving only the related changes.

@p7nov pls help with this. I don't know how should I resolve it, sorry :)