Resolve Wallet Encryption Vulnerability, Fix BLOK-32

[mcjcloud]

Replaces wallet signing of vault shards with encryption using PSK. The PSK works as a good encryption key because it

1. is a symmetric key that can be used for encryption and decryption
2. is always required to create an account/sign in
3. is shared between all devices, so no need to keep track of multiple encryption keys

Changes

• Replace shard signing with encryption
• Add a new encryptionKey property to motorNodeImpl

Fixes #680

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[prnk28]

@mcjcloud Next time lets use the branch provided by linear brayden/blok-32

[codecov-commenter]

Codecov Report

Base: 5.46% // Head: 5.59% // Increases project coverage by +0.12% 🎉

Coverage data is based on head (2bc937a) compared to base (6abf4b9).
Patch coverage: 53.84% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff            @@
##             dev    #713      +/-   ##
========================================
+ Coverage   5.46%   5.59%   +0.12%     
========================================
  Files        154     154              
  Lines      27979   27968      -11     
========================================
+ Hits        1530    1564      +34     
+ Misses     26294   26241      -53     
- Partials     155     163       +8     

Impacted Files	Coverage Δ
pkg/crypto/mpc/wallet.go	13.08% <0.00%> (+0.65%)	⬆️
pkg/motor/login.go	0.00% <0.00%> (ø)
pkg/motor/motor.go	29.29% <ø> (+3.82%)	⬆️
pkg/motor/create_account.go	42.28% <70.00%> (+16.13%)	⬆️
pkg/motor/create_bucket.go	11.90% <0.00%> (+11.90%)	⬆️

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