Use OTLP log exporter by default in otel-distro

[lmolkova]

See #2988 - to enable log export in the distro someone needs to:

• set OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED=true
• set OTEL_LOGS_EXPORTER=otlp

Let's default to OTLP exporter for logs and rely on OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED to guard logs configuration.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[xrmx]

@lmolkova please sort the imports :)