Add version methods

What does this MR do?

Add utility versions to interact with GitLab versions. Versions are fetched from two sources:

1. versions.gitlab.com => Used to interact with previous GitLab versions
2. releases.yml => Used to interact with upcoming GitLab releases

In this commit, three methods were added:

• active_version - To return the GitLab active version
• current_version - To return the GitLab current version
• next_versions - That returns the GitLab next patchable versions

Also execute was renamed to upcoming_releases

10:18:26 ❯ export PRODUCTION_TOKEN=glpat-123
10:18:27 ❯ irb
3.2.2 :001 > require 'release_dates'
 => true
3.2.2 :002 > release_dates = ReleaseDates
 => ReleaseDates
3.2.2 :003 > release_dates.upcoming_releases
 =>
{"16.2"=>"2023-07-22",
 "16.3"=>"2023-08-22",
 "16.4"=>"2023-09-22",
 "16.5"=>"2023-10-22",
 "16.6"=>"2023-11-16",
 "16.7"=>"2023-12-21",
 "16.8"=>"2024-01-18",
 "16.9"=>"2024-02-15",
 "16.10"=>"2024-03-21",
 "16.11"=>"2024-04-18",
 "17.0"=>"2024-05-16",
 "17.1"=>"2024-06-20",
 "17.2"=>"2024-07-18"}
3.2.2 :005 > release_dates.active_version
 => "16.3"
3.2.2 :006 > release_dates.current_version
 => "16.2"
3.2.2 :007 > release_dates.next_versions
 => ["16.2.5", "16.1.5", "16.0.9"]