Feature request: Add BZPOPMIN & BZPOPMAX support

[NickCraver]

These are new commands in Redis 5.0.0, requested in #1581:

• BZPOPMIN: https://redis.io/commands/bzpopmin
• BZPOPMAX: https://redis.io/commands/bzpopmax

These are the blocking versions of the already supported ZPOPMIN and ZPOPMAX commands. Like other blocking discussions such as #1474 (WAIT command), this is problematic in the pipeline approach and should probably share whatever very opt-in thing we do there.

[mgravell]

This is just OneMoreThing™ that would be enabled if I can find time to add a leased/pooled connection mode; I'd suggest we have some IPooledDatabase : IDatabase (or something, naming is hard) that adds all the blocking operations.

[dbarbashov]

Would much appreciate if this gets implemented