T2730
Depends on D12451
Stacked diff to localize existing uses of BCH.Mnemonic throughout the app and deprecate the BCH.Mnemonic object.
Pt 1/7 - Implement BCH.Mnemonic.toSeed locally
Pt 2/7 - Implement BCH.Mnemonic.generate locally
Pt 3/7 - Implement BCH.Mnemonic.wordLists locally
Pt 4/7 - Implement BCH.Mnemonic.validate locally
Pt 5/7 - Deprecate BCH.Mnemonic throughout the app
Pt 6/7 - Optimize bip39 bundle via webpack IgnorePlugin
Pt 7/7 - Unwrap validateMnemonicWordList