Support a specific version for the bundler input, and use the exact Bundler version from the lockfile if provided

• Fixes #123

Only set $BUNDLER_VERSION when needed

• Fixes #122

Add Ruby 3.0.0-preview2

• Fixes #121

Do not export BUNDLER_VERSION

• Fixes #119

Use CRuby releases from the toolcache when available

• See #98

Actually use Bundler 1 when specifying `bundler: 1` on Ruby 2.7+ and no lockfile

• Fixes #117

Actually use Bundler 1 when specifying `bundler: 1` on Ruby 2.7+

• Fixes #117
• This is a duplicate of v1.56.0, due to some error when creating the release on GitHub.

Try to match non-stable versions too like 3.0 for 3.0.0-preview1

GitHub Actions parses 3.0 as '3', so use quotes

* And adapt excludes.

Run bundle clean when reusing a cache and the lockfile changed

• Fixes #113

Add TruffleRuby 20.3.0

v1.52.0

Add TruffleRuby 20.3.0