use the same defaults for session pool config as in the sdk

[cardamo]

fixes #92

[nvamelichev]

@lavrukov Are you OK with the changes? Making an explicit default for session pool min size, instead of having min size=max size; and lowering idle time and default min/max pool size seem quite reasonable to me, and also align YOJ with the YDB Java SDK behavior.

I believe that anybody on the Right has either configured YDB session pool explicitly (if they care) or won't notice and/or care if the defaults change slightly.

[nvamelichev]

@cardamo Artem, let's take the pool defaults from SessionPoolOptions.DEFAULT constant in the SDK (it's public) if possible.
Otherwise LGTM

[cardamo]

nope, getters in tech.ydb.table.impl.pool.SessionPoolOptions are package-private 🤷‍♂️

[nvamelichev]

👎 After discussions with @lavrukov, I'm declining this PR as too risky for Right's Cloud Java (sorry).

• Short-term: We probably should change/enforce defaults in our libraries, instead.
• Also of note: Why the hell does YDB Java SDK not check that sessions are alive? Do we maybe need to make improvements there, or do we maybe need to enable some YDB Java SDK feature that will check sessions for liveness?