feat(cloudformation): Harden CloudFormation language-server installat… - #8856

…ion, caching, cleanup, and startup recovery while simplifying the installer abstraction layer

Problem

LSP downloads were inconsistent and insafe

Solution

• Resolve the highest compatible, non-delisted version for the current target.
• Adapt alpha, beta, and prod manifests only in the concrete CloudFormation adapter.
• Retry manifest and bundle downloads three times with exponential backoff.
• Parse manifests before atomic caching and fall back to the cached manifest when necessary.
• Validate hashes and required files before publication and again after post-install processing.
• Safely extract archives, delete ZIP files, and handle concurrent atomic publication.
• Retain the active version and highest valid fallback.
• Invalidate a failed managed installation and retry startup once.
• Replace the one-method ManifestProvider hierarchy with ResolveManifest function injection.
• Guard the cfn-init permission update when the optional executable is absent.
• Correct stale HttpResourceFetcher documentation.
• Preserve explicit restart and deactivation cleanup for client-session resources.

• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
• License: I confirm that my contribution is made under the terms of the Apache 2.0 license.