crypto: Simplify PrivateCrossSigningIdentity::with_account

[richvdh]

PrivateCrossSigningIdentity::with_account is called in lots of places where we end up throwing away most of its work. Indeed, there is only one place that actually uses the results (olm::Account::bootstrap_cross_signing).

It makes more sense to me to replace it with something similar, and hoist the remaining functionality up to bootstrap_cross_signing.

[codspeed-hq]

CodSpeed Performance Report

Merging #5654 will not alter performance

_{Comparing rav/identity_test_cleanups (0002ea4) with main (c2bc465)}

Summary

✅ 49 untouched

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.34%. Comparing base (4cc1cd1) to head (0002ea4).
⚠️ Report is 33 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5654      +/-   ##
==========================================
- Coverage   88.34%   88.34%   -0.01%     
==========================================
  Files         354      354              
  Lines       97098    97093       -5     
  Branches    97098    97093       -5     
==========================================
- Hits        85780    85772       -8     
- Misses       7265     7268       +3     
  Partials     4053     4053              

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[andybalaam]

I was just starting to write a rant about how with_account should not exist and then I read your second commit. Enthusiastic support here.

[poljar]

This was not a public method, as such this can't be a breaking change.

Do we now need to expose a public function for this?

[richvdh]

This was not a public method, as such this can't be a breaking change.

ohhh it was pub(crate), I missed that. And no, we don't need a public function. Let me have another go at this.

[richvdh]

@poljar I've made the new method pub(crate), and removed the changelog entry.