Update to sylabs/sif 2.15.1

[DrDaveD]

This cherry-picks the following PRs, bringing apptainer/sif up to date with sylabs/sif 2.15.1:

• fix: delete object sylabs/sif#327
• refactor: simplify zero implementation sylabs/sif#328
• feat: deprecate user package sylabs/sif#325
• build(deps): bump github.com/ProtonMail/go-crypto sylabs/sif#341

Original PR descriptions were
327:

A bug was discovered while deleting an object from a SIF, where the in-memory descriptor wasn't marked as unused.

This fixes that by simplifying the process by reseting the descriptor on the memory allocation, then calling writeDescriptors to persist the change to the backing SIF.

328:

Replace func zeroData with a simpler implementation that uses an io.Reader that streams zero bytes.

325:

Mark github.com/sylabs/sif/v2/pkg/user package deprecated. Remove experimental mount and unmount commands.

Closes sylabs/sif#323

341:
No description provided.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (384ce86) 72.83% compared to head (ceb19fa) 73.06%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/sif/create.go	75.00%	2 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
+ Coverage   72.83%   73.06%   +0.23%     
==========================================
  Files          35       31       -4     
  Lines        2974     2918      -56     
==========================================
- Hits         2166     2132      -34     
+ Misses        648      630      -18     
+ Partials      160      156       -4     

Flag	Coverage Δ
unittests	73.06% <75.00%> (+0.23%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.