FFI: Expose ed25519/curve25519 keys in bindings

[BillCarsonFr]

The Element-X rageshakes are lacking device keys info, see element-hq/element-x-ios#2550

This change exposes these so that it can be used by the app.
The ed25519_key() was already present in the sdk but not exposed in bindings. I added a second one for curve25519_key() in both sdk and bindings.

Can be accessed via client.encryption().curve25519Key() in the aps

• Public API changes documented in changelogs (optional)

Signed-off-by:

[bnjbvr]

Please follow the contribution guidelines when it comes to PR names.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 82.97%. Comparing base (cbb92ca) to head (f5cddec).
Report is 20 commits behind head on main.

Files	Patch %	Lines
crates/matrix-sdk/src/encryption/mod.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3420      +/-   ##
==========================================
- Coverage   82.98%   82.97%   -0.02%     
==========================================
  Files         246      246              
  Lines       25011    25012       +1     
==========================================
- Hits        20756    20754       -2     
- Misses       4255     4258       +3     

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thanks for updating the title!

[poljar]

Could you make CI happy? I think that this is should be a pretty trivial change, but CI failures need to be addressed.

[BillCarsonFr]

Could you make CI happy? I think that this is should be a pretty trivial change, but CI failures need to be addressed.

Oh sry, I missed the failing checks