internal/config: migrate local config to .git/glab-cli

[profclems]

To set a local config, glab writes to .glab-cli/config/config.yaml and to hide it, writes to .gitignore.

This change migrates the local config to .git/glab-cli to avoid messing with the .gitignore of the current project.

Resolves #791 #384

[codecov]

Codecov Report

Merging #813 (a9ec9d7) into trunk (b8a02b5) will decrease coverage by 0.15%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##            trunk     #813      +/-   ##
==========================================
- Coverage   59.45%   59.29%   -0.16%     
==========================================
  Files          93       93              
  Lines        7357     7353       -4     
==========================================
- Hits         4374     4360      -14     
- Misses       2601     2613      +12     
+ Partials      382      380       -2     

Impacted Files	Coverage Δ
internal/config/config_migration.go	0.00% <0.00%> (ø)
internal/config/config_type.go	69.45% <ø> (ø)
internal/config/file.go	100.00% <ø> (+12.90%)	⬆️
internal/config/local_config.go	31.81% <100.00%> (+5.73%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b8a02b5...a9ec9d7. Read the comment docs.

[zemzale]

LGTM!