Clean up standalone-repo artifacts from inlined iac/

Remove files that are unnecessary now that iac/ lives inside the monorepo:
- .github/ (workflows, issue templates, dependabot, labeler, action dist)
- .gitmodules (empty tree-sitter submodule refs, deps pulled via Cargo)
- .gitignore, .gitattributes (parent repo covers these)
- .release.yml, .all-contributorsrc (standalone release/contributor configs)
- action.yml (GitHub Action for standalone use)
- .vscode/ (IDE settings for standalone dev)
- CODE_OF_CONDUCT.md, CONTRIBUTING.md, SECURITY.md, SUPPORT.md (parent has these)
- scripts/publish-extractor-pack.sh, scripts/install-extractor.sh (standalone distribution)
- Empty tree-sitter-hcl/, tree-sitter-dockerfile/ submodule dirs

Also fix stale iac/lib/src/qlpack.yml path in codeql-workspace.yml.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 3c4d8373-31fc-4727-bcdb-94c778ee07bd

Author: chanel-y

codeql-workspace.yml

@@ -19,7 +19,6 @@ provide:
   - "misc/suite-helpers/qlpack.yml"
   - ".github/codeql/extensions/**/codeql-pack.yml"
   - "actions/ql/extensions/**/qlpack.yml"
-  - "iac/lib/src/qlpack.yml"
   - "iac/ql/src/qlpack.yml"
 versionPolicies:
   default: