[Cashtab] Improve isValidStoredWallet validation

Summary: As per feedback from D14186, updating isValidStoredWallet validation logic to also check for name, mnemonic, Path245, Path145 and Path1899 keys in the wallet object.

Test Plan: npm test

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D14190