minimum LogLevel is not well implemented

[sproctor]

First, the docs are not clear what SupabaseClientBuilder.defaultLogLevel does. I assume it's the level at and above which log messages are not ignored. I think the docs should be updated to make that explicit.

Second, Kermit has its own config for this. If you set a global minSeverity, the higher of that and the one set in SupabaseClientBuilder will be the observed value. If I want to set the default minSeverity to Info for my other loggers, but override that to Debug for Supabase loggers, that doesn't appear to be possible. In KermitSupabaseLogger, when level is set, it should set logger.mutableConfig.minSeverity, including during initialization.`

Do you agree with this and want me to make a PR?