Linter: `Collection` suffix should be renamed to `Group`/`List`

Parent: #4442

## Convention

Rename `Collection` to `Group` or `List` when it makes sense (and does not conflict with existing models). Domain exceptions like `MongoDBCollection` are allowed.

> Source: [Azure SDK for .NET Mgmt Naming Conventions](https://github.com/Azure/azure-sdk-for-net/blob/main/doc/dev/Mgmt-Naming-Conventions.md)

## Observed today

A scan of `Azure/azure-rest-api-specs` (334 `client.tsp` files, 10,754 csharp-scoped `@@clientName` decorators) shows **0** decorators currently encoding this rule by hand. Examples:

_(no observed renames yet)_

## Proposed linter

**Detection**

Flag any model whose name ends with `Collection`. Allow opt-out for known domain terms via a `known-collection-names` rule config.

**Auto-fix**

Suggest `Group` (default) or `List` rename via `@@clientName`.

**Scope**

The rule should be csharp-scoped — it only flags violations of the .NET convention, not the underlying TypeSpec name. It should suggest inserting a `@@clientName(..., "csharp")` override when the underlying TypeSpec name is intentional, or renaming the TypeSpec model when the convention applies cross-language.

## Acceptance criteria

- [ ] New lint rule registered in the appropriate ruleset (`@azure-tools/typespec-client-generator-core` or `@azure-tools/typespec-azure-resource-manager`).
- [ ] Doc page under `website/src/content/docs/docs/libraries/.../rules/`.
- [ ] Unit tests covering positive / negative cases and the auto-fix.
- [ ] A `.chronus/changes/` entry.

Start by inspecting existing lint rules and ruleset registration in @azure-tools/typespec-client-generator-core and @azure-tools/typespec-azure-resource-manager. Then review the rule documentation under website/src/content/docs/docs/libraries/.../rules/ and existing unit tests for positive, negative, and auto-fix patterns. Done means the rule, documentation, tests, and a .chronus/changes/ entry satisfy the acceptance criteria.

Written by the indexing model from the issue text.