[MSD benchmark] Plugins: Chore: Renamed instrumentation middleware to metrics middleware

[khaliqgant]

MSD benchmark PR recreated from Martian Code Review Bench.

Source PR: grafana#76186
Dataset: grafana
Original title: Plugins: Chore: Renamed instrumentation middleware to metrics middleware

What is this feature?

• Renames the InstrumentationMiddleware to MetricsMiddleware
• Moves the contextual logger from the Instrumentation/Metrics middleware to the LoggerMiddleware

Why do we need this feature?

Better naming and consistency.

Who is this feature for?

Plugins platform.

Which issue(s) does this PR fix?:

Fixes #

Special notes for your reviewer:

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.