Resolve microsoft#19985.

Deprecates the logging level setting. The default for logging level from
VS Code is Info, so in this PR moved a few items to verbose so that we
get the same logging experience.

Closes microsoft#20844

…oft#21062)

In this PR:
1. Changes the python extension logging to use LogOutputChannel
2. Changes the language server logger with LogOutputChannel
3. Test output channel uses OutputChannel as it needs to show test
output and not really logging. Also, using logging test output makes it
pretty much unreadable.
4. Simplifies logging channel and output channel registration.

We need to do this now to make it easier for new test work to integrate
with output logging.

For microsoft#20844

This still doesn't get rid of the log level setting.

fixes microsoft#21122

Reverts microsoft#21048

Closes microsoft#21146
Related microsoft#19985