Allow connection settings to be applied asyncronously

[michel-laterman]

Expose SetConnectionsSettingsStatus method in client interface to allow implementations that use async approaches to connection management to succeed instead of automatically setting APPLIED.

This change technically breaks an assumption we had in the initial implementation and passes the responsibility for setting the connectionsettingsstatus to the callback implementation.

The client/internal/receivedprocessor.go still sets the status to APPLYING if any connection settings are sent (and the reports connections settings status capability is set),

• Relates: [cmd/opampsupervisor] opamp supervisor do not send ConnectionSettingsStatus in message after OfferedConnectionSettings opentelemetry-collector-contrib#46157

[codecov]

Codecov Report

❌ Patch coverage is 90.47619% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.10%. Comparing base (03800d0) to head (4d5f22b).

Files with missing lines	Patch %	Lines
client/internal/clientcommon.go	88.23%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #544      +/-   ##
==========================================
+ Coverage   82.38%   85.10%   +2.72%     
==========================================
  Files          28       28              
  Lines        2208     2189      -19     
==========================================
+ Hits         1819     1863      +44     
+ Misses        264      203      -61     
+ Partials      125      123       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[michel-laterman]

@tigrannajaryan @evan-bradley, I'm addressing the changes needed in opamp-go for open-telemetry/opentelemetry-collector-contrib#46157

This is a pretty fundamental change as it changes what sets the status from an internal detail (that assumes the callback is synchronous), to something that the connection settings callbacks needs to explicitly set