CryptoV2 changes

[Anderas]

A number of changes to rust-based Crypto V2 after extensive testing with polyjuice:

• expose VerificationState on decryption result to display trusted / untrusted sessions
• ensure CryptoV2 gets initialized on the main queue
• move event observers from key verification manager to crypto v2 to gain access to downloading user keys and processing outgoing requests
• always download keys for new senders before processing to-device events
• restore room keys from backup after recieving recovery key

[codecov]

Codecov Report

Base: 36.37% // Head: 15.88% // Decreases project coverage by -20.49% ⚠️

Coverage data is based on head (4174724) compared to base (befcd80).
Patch coverage: 11.14% of modified lines in pull request are covered.

Additional details and impacted files

@@                    Coverage Diff                    @@
##           andy/complete_crypto    #1622       +/-   ##
=========================================================
- Coverage                 36.37%   15.88%   -20.50%     
=========================================================
  Files                       577      578        +1     
  Lines                     90876    91061      +185     
  Branches                  39535    38397     -1138     
=========================================================
- Hits                      33056    14464    -18592     
- Misses                    56837    76118    +19281     
+ Partials                    983      479      -504     

Impacted Files	Coverage Δ
...trixSDK/Crypto/CryptoMachine/MXCryptoMachine.swift	0.00% <0.00%> (ø)
...chine/MXEventDecryptionResult+DecryptedEvent.swift	0.00% <0.00%> (ø)
MatrixSDK/Crypto/KeyBackup/MXKeyBackup.m	0.00% <0.00%> (-62.14%)	⬇️
MatrixSDK/Crypto/MXCryptoV2.swift	0.79% <0.00%> (-0.13%)	⬇️
...K/Crypto/SecretStorage/MXCryptoSecretStoreV2.swift	0.00% <0.00%> (ø)
MatrixSDK/JSONModels/MXJSONModels.m	6.63% <0.00%> (-20.52%)	⬇️
MatrixSDK/MXSession.m	7.96% <0.00%> (-32.01%)	⬇️
...rypto/CryptoMachine/MXCryptoMachineUnitTests.swift	0.00% <0.00%> (ø)
...ypto/Verification/MXKeyVerificationManagerV2.swift	27.77% <10.00%> (-1.31%)	⬇️
...s/Crypto/CryptoMachine/MXCryptoProtocolStubs.swift	51.31% <12.50%> (-2.11%)	⬇️
... and 196 more

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[paleksandrs]

Looks good to me. Do you need to add a changelog for this?

[Anderas]

Looks good to me. Do you need to add a changelog for this?

Its pretty much bugfixes for #1620, I just did not want to do it in the same PR for readability, so I don't think changelog is necessary