Set local trust with Crypto V2 and deprecate legacy verification method

[Anderas]

A few final bits to implement CryptoV2:

• set local trust (incl (un)blacklisting users)
• remove deprecated and legacy verification method that does not begin with verification request (use requestVerificationWithDevice instead)
• determine room encryption state
• retry decryption of events after manually importing keys

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@5960e8b). Click here to learn what that means.
Patch coverage: 14.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #1613   +/-   ##
==========================================
  Coverage           ?   15.77%           
==========================================
  Files              ?      575           
  Lines              ?    90921           
  Branches           ?    38355           
==========================================
  Hits               ?    14347           
  Misses             ?    76107           
  Partials           ?      467           

Impacted Files	Coverage Δ
...trixSDK/Crypto/CryptoMachine/MXCryptoMachine.swift	0.00% <0.00%> (ø)
MatrixSDK/Crypto/MXCryptoV2.swift	0.80% <0.00%> (ø)
...SDK/Crypto/Verification/MXKeyVerificationManager.m	0.00% <ø> (ø)
...s/Crypto/CryptoMachine/MXCryptoProtocolStubs.swift	54.10% <0.00%> (ø)
...fication/MXKeyVerificationManagerV2UnitTests.swift	89.28% <ø> (ø)
MatrixSDKTests/MXCryptoKeyVerificationTests.m	0.00% <ø> (ø)
...ypto/Verification/MXKeyVerificationManagerV2.swift	28.86% <19.23%> (ø)
...fication/Transactions/SAS/MXSASTransactionV2.swift	54.96% <100.00%> (ø)
...Transactions/SAS/MXSASTransactionV2UnitTests.swift	100.00% <100.00%> (ø)

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[stefanceriu]

Apart from one small comment lgtm 👍