WIP: ILogger for ConnectionMultiplexer

[NickCraver]

Working on ILogger support, but without new overloads possibly. Since we support Action<ConfigurationOptions> this can be added today e.g. with o => o.Logger = myLogger:

var muxer = ConnectionMultiplexer.Connect("localhost", o => o.Logger = myLogger);

...or we could add sibling overloads to the existing TextWriter. I'd love to not create a ^2 matrix every time we do this, though. Starting simpler for that reason. Note: this is on top of #2050 for simplicity, will roll against main when merged.

TODOs here:

• [ ] General sanity check
• [ ] Overloads decision
• [ ] Tests of this implementation
• [ ] Seeing which additional things need logging, we should make a list and check it here.