feat(sdk): Add support for refresh tokens

[zecakeh]

Refresh tokens are for when access tokens have an expiry date. It allows to request a new access token without logging again. It's part of the spec since v1.3 and is a prerequisite for #859.

Some refactoring of Session was necessary to be able to make the tokens mutable. We could use a single method to expose the tokens as ReadOnlyMutable in the client, but I thought it would be easier to grasp it with separate methods for users that don't know how the futures-signals crate works.

We give the option for the Client to refresh the tokens automatically. It's not enabled by default to be conservative and avoid the user holding an obsolete refresh token.

[codecov]

Codecov Report

Merging #892 (deae3f7) into main (ae261c2) will increase coverage by 0.45%.
The diff coverage is 96.79%.

@@            Coverage Diff             @@
##             main     #892      +/-   ##
==========================================
+ Coverage   79.38%   79.83%   +0.45%     
==========================================
  Files         106      107       +1     
  Lines       14662    15052     +390     
==========================================
+ Hits        11639    12017     +378     
- Misses       3023     3035      +12     

Impacted Files	Coverage Δ
crates/matrix-sdk-appservice/src/virtual_user.rs	48.97% <0.00%> (-1.03%)	⬇️
crates/matrix-sdk/src/error.rs	25.92% <ø> (ø)
crates/matrix-sdk/tests/integration/main.rs	100.00% <ø> (ø)
crates/matrix-sdk/src/client/login_builder.rs	27.10% <50.00%> (+1.85%)	⬆️
crates/matrix-sdk/src/client/mod.rs	76.01% <88.33%> (+1.55%)	⬆️
crates/matrix-sdk-base/src/session.rs	66.66% <90.90%> (+66.66%)	⬆️
crates/matrix-sdk-base/src/client.rs	79.47% <100.00%> (+0.41%)	⬆️
crates/matrix-sdk-base/src/store/mod.rs	88.88% <100.00%> (+1.38%)	⬆️
crates/matrix-sdk/src/client/builder.rs	81.73% <100.00%> (+0.92%)	⬆️
crates/matrix-sdk/tests/integration/client.rs	94.75% <100.00%> (+0.48%)	⬆️
... and 1 more

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[jplatte]

Didn't fully review, just a small note

[jplatte]

I think poljar had some thoughts on this, though let me know if I should do a full review.

[gnunicorn]

Thanks heaps. In particular appreciate all these tests!

Two things need to change though:

1. naming things: I find SessionIds confusing, maybe we can opt of SessionInfo or SessionMeta instead?
2. changing Session means we need to add migrations for the stores to prevent a forced login when coming with an old. Would be great to add an integration test for it. You think you'll be able to add migrations for the stores?

[gnunicorn]

Ignore my migration request, only the error passing missing, the this is ready for merge IMHO.

[zecakeh]

This force push was to rebase on main because GitHub complained there was a conflict.