Remove Freezer from inactive state

This patch proposes to re-establish a Freezer as Active project. During
inactivity following issues were addressed:

* CI health recovered for remaining repositories [1][2][3][4][5]
* Proposed to retire freezer-dr project to focus on main project objective [6]
* Re-established access to #openstack-freezer IRC channel
* Slightly updated docs to include more necessary infromation about
the project for potential users

There are still ongoing activities to fuly put back project back on
rails, like moving bug tracker back to launchpad [7], though given that
we've passed a milestone-2, where clients should be released [8],
it's already time to decide if Epoxy should be considered as a release
for marking Freezer as active project again.

[1] https://review.opendev.org/q/project:openstack/freezer
[2] https://review.opendev.org/q/project:openstack/freezer-api
[3] https://review.opendev.org/q/project:openstack/python-freezerclient
[4] https://review.opendev.org/q/project:openstack/freezer-tempest-plugin
[5] https://review.opendev.org/q/project:openstack/freezer-web-ui
[6] https://lists.openstack.org/archives/list/openstack-discuss@lists.openstack.org/message/3VQUSJHBOOH3MKIMHUINNV75REF3GS7Z/
[7] https://lists.openstack.org/archives/list/openstack-discuss@lists.openstack.org/message/7PD7TVDLSHVXL7O7HFDVQXAZVW2EUV4G/
[8] https://review.opendev.org/c/openstack/releases/+/938780

Change-Id: Ib34b6f91cfd6134e695b768fbbac226b930017ad

reference/emerging-technology-and-inactive-projects.rst

@@ -129,8 +129,3 @@ Current Inactive Projects
 
   * Inactive since 2024.1 cycle
   * Extension in 2024.2 cycle
-
-* Freezer
-
-  * Inactive since 2024.1 cycle
-  * Extension in 2024.2 cycle