build-aux/snap, .github/workflows: bump go snap version for building and testing snapd snap

[ernestl]

Bump the version of go snap used for building and testing snapd snap

Overview:

• Static checks and unit tests run with both (1) the go channel that snapd snap is build with and (2) and latest/stable
• Avoid manual workflow changes for channel updates, by looking up snapd build go channel from snapcraft.yaml
• Also supports looking up Go snap channel for snapd FIPS
• Avoid job duplication if versions are the same e.g. "1.23/stable" and "latest/stable"
• Avoid manual branch "required" maintenance by using statically named gatekeepers for unit test and static checks that always run and evaluate all results even if dependencies are skipped

Take note:

• Temp intentional unit test failure do demonstrate more dynamic "required" solution
• Open question on if/how exactly we want to test for FIPS
• There are a lot of cancelled required tests, this is expected given the change, and will be solved by simplifying branch rules after landing the PR.

Addtional Info:

• Spread run of unit tests: https://paste.ubuntu.com/p/x4XG6SM4zr/

Jira: https://warthogs.atlassian.net/browse/SNAPDENG-33212

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.20%. Comparing base (96ea7b0) to head (c969f94).
Report is 102 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #14752      +/-   ##
==========================================
- Coverage   78.95%   78.20%   -0.75%     
==========================================
  Files        1084     1148      +64     
  Lines      146638   151144    +4506     
==========================================
+ Hits       115773   118200    +2427     
- Misses      23667    25626    +1959     
- Partials     7198     7318     +120     

Flag	Coverage Δ
unittests	78.20% <ø> (-0.75%)	⬇️

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