Use a defined list of locations to search for bundler version

What does this Merge Request do and why?

Use a pre-defined list of locations to check for the BUNDLED WITH version, instead of a find ..

We don't need to install any version older than 2.x, and in 2.x we can safely use the latest as it is backward/foreward compatible.

This version runs much faster.

Before:

bash-3.2$ time find . -type f -name Gemfile.lock -exec awk '/BUNDLED WITH/{getline;print $NF;}' {} + 2> /dev/null | sort -r | uniq
2.2.29
2.1.4
1.17.3

real	0m5.284s
user	0m0.268s
sys	0m5.012s

After:

bash-3.2$ time find ${gemfiles[*]} -type f -name Gemfile.lock -exec awk '/BUNDLED WITH/{getline;print $NF;}' {} + 2> /dev/null | sort -r | head -n 1
2.1.4

real	0m0.013s
user	0m0.008s
sys	0m0.010s

(the projects that are bundled with 2.2.x above will work in 2.1.x. See #1378 (closed) for a list of them)

Fixes #1378 (closed)

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.