Add btrfs support in partitioner

[davidcassany]

Part of #1874

[codecov-commenter]

Codecov Report

Attention: 359 lines in your changes are missing coverage. Please review.

Comparison is base (840c80c) 75.96% compared to head (a6892f5) 72.53%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
pkg/action/mount.go	5.94%	169 Missing and 5 partials ⚠️
cmd/config/config.go	3.50%	55 Missing ⚠️
pkg/config/config.go	15.78%	48 Missing ⚠️
pkg/types/v1/config.go	0.00%	28 Missing ⚠️
cmd/mount.go	23.07%	19 Missing and 1 partial ⚠️
pkg/features/features.go	18.75%	12 Missing and 1 partial ⚠️
pkg/partitioner/disk.go	65.38%	6 Missing and 3 partials ⚠️
pkg/constants/constants.go	0.00%	7 Missing ⚠️
pkg/systemd/unit.go	0.00%	3 Missing ⚠️
cmd/build-disk.go	0.00%	1 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1878      +/-   ##
==========================================
- Coverage   75.96%   72.53%   -3.44%     
==========================================
  Files          66       69       +3     
  Lines        6912     7286     +374     
==========================================
+ Hits         5251     5285      +34     
- Misses       1290     1622     +332     
- Partials      371      379       +8     

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[kkaempf]

lgtm