My application spends more than 30% of time during `bundle update`
comparing versions due to versions being sorted inside
next_package_to_try. This has been addressed in pub_grub by defining a
strategy interface (a `#next_package_and_version` method) which allows
consumers to have finer control over the heuristic to select the next
package to try.

This commit implements the new strategy interface to remove extraneous
version sorting (previously in next_package_to_try) since only the final
count of versions is used.

Combined with a previous change to pub_grub (already applied to
Bundler), this commit results in `bundle update` taking only half the
time it did on 2.6.5.

https://github.com/rubygems/rubygems/commit/62f69e27f0

https://github.com/rubygems/rubygems/commit/3aaa75e7b9

https://github.com/rubygems/rubygems/commit/c38a96ceae

Helps ensure that unsuspecting diffs to the vendored code arent accidentally introduced

https://github.com/rubygems/rubygems/commit/7c425d49dd

  Pick from https://github.com/rubygems/rubygems/commit/7a7b234721c375874b7e22b1c5b14925b943f04e

  Pick from https://github.com/rubygems/rubygems/commit/e9304aed7e43308b99e70c2f7b92028315fee8a5

* Replaces the wording of "is forbidden" with "cannot be used"
* Fixes the method signature of VersionRange::Empty#eql?

https://github.com/rubygems/rubygems/commit/8c6b3f130b

Co-authored-by: Daniel Colson <danieljamescolson@gmail.com>

We became a bit out of sync lately.

https://github.com/rubygems/rubygems/commit/6161a2610a

  from https://github.com/rubygems/rubygems/commit/0635c1423db5d7c461d53bf0c3329bca75de7609