Consolidate connection comparison helpers under ConnectionMatcher

## Problem

Connection comparison behavior is currently split across standalone helpers in models/utils.ts and the ConnectionMatcher class. This makes the available matching contracts harder to discover and encourages feature-specific helpers such as isSameScmpConnection.

This follow-up was identified during review of #22877.

## Proposed change

- Move the exported profile and connection equality helpers onto ConnectionMatcher.
- Give the database-independent comparison a feature-neutral name that describes its behavior.
- Preserve the existing comparison semantics for current consumers.
- Update all call sites and add focused tests documenting each comparison contract.

## Acceptance criteria

- ConnectionMatcher is the single public entry point for connection/profile comparison logic.
- No existing standalone equality helpers remain exported.
- The database-independent comparison is reusable outside Schema Compare.
- Existing callers compile and focused matcher tests pass.

Start in models/utils.ts and inspect the existing helpers alongside ConnectionMatcher to map each comparison contract and its current callers. Update the call sites and add focused matcher tests covering the documented contracts; done means ConnectionMatcher is the single public entry point, standalone equality helpers are no longer exported, and existing callers compile.

Written by the indexing model from the issue text.