Replace archived matrix-org/gomatrix dependency

[Johennes]

This switches from https://github.com/matrix-org/gomatrix (which is archived) to https://github.com/mautrix/go.

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[codecov]

Codecov Report

❌ Patch coverage is 53.84615% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.91%. Comparing base (c9c4687) to head (b33f290).

Files with missing lines	Patch %	Lines
fclient/federationclient.go	25.00%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #466   +/-   ##
=======================================
  Coverage   53.90%   53.91%           
=======================================
  Files          52       52           
  Lines        6025     6026    +1     
=======================================
+ Hits         3248     3249    +1     
  Misses       2363     2363           
  Partials      414      414           

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[Johennes]

Looks like this won't be as straightforward as I thought because apparently dendrite would require changes, too.

[kegsay]

LGTM, though I suspect this is a breaking change as users of this library will type assert gomatrix errors.

[Johennes]

Yeah. 😕 Not sure how to avoid that though?

[S7evinK]

iirc, we tried to never break Dendrite but didn't really care about gmsl.
If Dendrite works with this change, LGTM. Given the unit tests are failing, I'd be cautious.

[Johennes]

This is for testing and demonstration purposes only and needs to be removed before merging.

[Johennes]

I don't see a way to not break dendrite due to the type change. I've now downgraded mautrix/go to the same version used in dendrite and opened element-hq/dendrite#3708 to replace matrix-org/gomatrix in dendrite, too.