CHEF-35092 - Use appbundler for habitat packaging

[sanjain-progress]

Description

This pull request improves the packaging and installation process for chef-vault in Habitat environments. The main changes include switching to appbundler for binstub generation, cleaning up vendored gems to avoid CVE false positives, and simplifying the Habitat install script.

Packaging and binstub improvements

• Overhauled habitat/plan.sh to generate binstubs using appbundler with precise version pins, replacing the previous wrap_ruby_bin wrapper function
• Added binstub_patch.rb to configure APPBUNDLER_ALLOW_RVM and GEM_PATH at runtime, allowing binstubs to run directly
• Replaced do_setup_environment() with push_runtime_env/set_runtime_env pattern for proper Habitat runtime environment setup
• Added do_prepare() to create /usr/bin/env symlink when missing
• Added do_end() to clean up the /usr/bin/env symlink after build
• Created libexec/ wrapper pattern: binstub is moved to libexec/ and a bash wrapper in bin/ sets up PATH, GEM_HOME, GEM_PATH before exec
• Added core/sed to pkg_build_deps

Vendored gem cleanup

• Added cleanup_lint_roller.rb script to remove stray Gemfile.lock files from vendored gems (lint_roller, stackprof-webnav, chef-vault) to appease security scanners
• Added .github directory removal in habitat/plan.sh (do_after) and habitat/plan.ps1 (Invoke-After) to avoid CVE false positives from vendored gem metadata

Build/test process improvements

• Simplified Habitat installation in .expeditor/buildkite/artifact.habitat.test.ps1 by removing explicit version pinning ($HabitatVersion) and always installing the latest Habitat
• Simplified Install-Habitat function to a single Invoke-Expression call
• Removed redundant project root logging from Windows test script

Files changed

File	Change
binstub_patch.rb	New — Runtime GEM_PATH configuration for binstubs
cleanup_lint_roller.rb	New — Removes stray Gemfile.lock from vendored gems
habitat/plan.sh	Modified — Appbundler pattern, lifecycle hooks, .github cleanup
habitat/plan.ps1	Modified — .github directory cleanup in Invoke-After
.expeditor/buildkite/artifact.habitat.test.ps1	Modified — Simplified Habitat install, removed verbose logging

Types of changes

• Chore (non-breaking change that does not add functionality or fix an issue)

Checklist

• I have read the CONTRIBUTING document.
• All new and existing tests passed.
• All commits have been signed-off for the Developer Certificate of Origin.

[github-actions]

Simplecov Report

Covered	Threshold
98.57%	90%