Add register to proxy scc support for Agama

[rfan1]

https://progress.opensuse.org/issues/177729

• Verification run:
  x86_64-BM
  powerVM

bare-metal5:~ # suseconnect -s
[{"name":"SUSE Employee subscription for SUSE Linux Enterprise Server x86_64","identifier":"SLES","version":"16.0","arch":"x86_64","status":"Registered","regcode":"xxxxxxxxxxxxx","starts_at":"2024-12-16 12:48:17 UTC","expires_at":"2025-12-16 12:48:17 UTC","subscription_status":"ACTIVE","type":"internal"}]
bare-metal5:~ # zypper lr -u
Repository priorities are without effect. All enabled repositories share the same priority.

# | Alias                                                                 | Name                         | Enabled | GPG Check | Refresh | URI
--+-----------------------------------------------------------------------+------------------------------+---------+-----------+---------+-----------------------------------------------------------------------------
1 | SUSE_Linux_Enterprise_Server_16.0_x86_64:SLE-Product-SLES-16.0        | SLE-Product-SLES-16.0        | Yes     | (r ) Yes  | Yes     | http://openqa.suse.de/assets/repo/SLES-Packages-16.0-x86_64-Build5.1/
2 | SUSE_Linux_Enterprise_Server_16.0_x86_64:SLE-Product-SLES-16.0-Debug  | SLE-Product-SLES-16.0-Debug  | No      | ----      | ----    | http://openqa.suse.de/assets/repo/SLES-Packages-16.0-x86_64-Debug-Build5.1/
3 | SUSE_Linux_Enterprise_Server_16.0_x86_64:SLE-Product-SLES-16.0-Source | SLE-Product-SLES-16.0-Source | No      | ----      | ----    | http://openqa.suse.de/assets/repo/SLES-Packages-16.0-x86_64-Source-Build5.1/

[github-actions]

Great PR! Please pay attention to the following items before merging:

Files matching lib/**.pm:

• Consider adding or extending unit tests in t/

This is an automatically generated QA checklist based on modified files.

[Julie-CAO]

Great! We are going to replace official scc server with the proxy scc when your PR is merged.

[rfan1]

Pending issue:
s390x fatal issue https://bugzilla.suse.com/show_bug.cgi?id=1237527 so we can't move forward now

[rfan1]

Please DONOT merge so far, as we have to make sure the features are ready for production build as well

[czerw]

LGTM for ipxe_install

[Amrysliu]

LGTM