Improve package manager detection for Bun 1.2 compatibility

[r3cha]

I'm using bun and install packages with bun install --yarn and its generate a yarn.lock file, same time new version of bun 1.2 generates bun.lock file instead of bun.lockb.
Some users may have bun with yarn.lock file or bun with bun.lock

My assets recompilation failed with:

RAILS_ENV=production rails assets:precompile
bin/rails aborted!
cssbundling-rails: Command install failed, ensure yarn is installed

Tasks: TOP => assets:precompile => css:build => css:install
(See full trace by running task with --trace)

Here is a proposal to handle this, idk what best way to do this. If this way looks ok I can fix test as well. Also we have using_bun? method at Helpers module that dose not check for bun.lock and return false if bun exists and yarn.lock present

• Add support for both old bun.lockb and new bun.lock Bun lock files
• Handle Bun with Yarn compatibility mode yarn.lock
• Combine command existence and lock file checks into single method