Add user profile tests, refactor user API methods

[S7evinK]

This adds tests for /profile.
Also, as a first change in this regard, refactors the methods defined on the UserInternalAPI to not use structs as the request/response parameters.

[codecov]

Codecov Report

Patch coverage: 62.65% and project coverage change: +0.10 🎉

Comparison is base (2854ffe) 65.95% compared to head (7853548) 66.05%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3030      +/-   ##
==========================================
+ Coverage   65.95%   66.05%   +0.10%     
==========================================
  Files         495      495              
  Lines       53642    53580      -62     
==========================================
+ Hits        35377    35394      +17     
+ Misses      14625    14556      -69     
+ Partials     3640     3630      -10     

Flag	Coverage Δ
unittests	44.76% <62.65%> (+0.21%)	⬆️

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

Impacted Files	Coverage Δ
clientapi/routing/server_notices.go	65.86% <0.00%> (-4.66%)	⬇️
clientapi/threepid/invites.go	6.56% <0.00%> (+0.19%)	⬆️
federationapi/routing/threepid.go	0.00% <0.00%> (ø)
internal/eventutil/types.go	62.50% <ø> (ø)
userapi/api/api.go	70.90% <ø> (ø)
federationapi/routing/profile.go	61.22% <50.00%> (-6.09%)	⬇️
appservice/api/query.go	57.89% <60.00%> (+0.75%)	⬆️
userapi/internal/user_api.go	61.77% <81.81%> (-0.46%)	⬇️
clientapi/routing/profile.go	54.09% <84.61%> (+18.46%)	⬆️
clientapi/routing/joinroom.go	88.40% <100.00%> (+1.26%)	⬆️
... and 2 more

... and 22 files with indirect coverage changes

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