Analyzers for MSBuild task authors

It is not easy for Task authors cannot to tell by reading their own code whether it is safe to run on a thread. Analyzers find these problems at build time instead: process-wide state, unsafe path handling, and APIs that are never safe inside a task. Without them, migrating the task ecosystem to multithreaded mode depends on manual review.

This epic covers all analyzer work, from shipping the first release to the enhancements that follow.

## Steps

- [ ] [#14078](https://github.com/dotnet/msbuild/issues/14078) Ship the analyzers to task authors [size L] [Milestone: version 18.12]
- [ ] [#14772](https://github.com/dotnet/msbuild/issues/14772) Enhance the analyzers and fix the bugs after shipping [size XL] [Milestone: SDK 11.0.200]

## Stakeholders

Task authors in dotnet/sdk, dotnet/nuget, dotnet/roslyn, dotnet/arcade and the VMR, plus task authors referencing latest `Microsoft.Build.Framework`.

## Definition of done

Task authors get the analyzers automatically with MSBuild, and the analyzers catch the unsafe patterns that task migration has actually hit.

Start by reading linked issues #14078 and #14772, which divide shipping the analyzers from later enhancements and bug fixes. Use the listed unsafe patterns and definition of done to determine the specific analyzer scope; completion means analyzers ship automatically with MSBuild and catch unsafe patterns found during task migration.

Written by the indexing model from the issue text.