Add SkipEnabledCheck=true to ConnectionSelected log message

[LeaFrock]

Summary

Avoid unnecessary double enabled check.

Motivation

Closes #661

Changes

• Add SkipEnabledCheck = true to LogMessages.ConnectionSelected

Checklist

• Code compiles without warnings (TreatWarningsAsErrors is enabled)
• Tests pass locally (dotnet test)
• New code has test coverage
• No breaking changes to public API (or documented in PR description)

[imperugo]

Thanks @LeaFrock — merging this.

The // Check by the caller comment is exactly what this needed: SkipEnabledCheck = true turns "the caller guards" into a contract, and without that note the next person to add a call-site would silently pay the full formatting cost on the hottest path in the library. Good catch on the two stale usings too — the Core.Extensions one was left over from the MinBy removal in #659.

This ships with the v13.5 release, once the rest of that milestone lands.