feat: Extension - Add view and import Spending Key

[jurevans]

Resolves #1720

• User can import Spending Key (similar to Private Key import)
• User can view Spending Key
• User is prompted to authenticate to view Spending Key (similar to View Seed Phrase)

Testing

NOTE I think it's a good idea while running this locally, to take an existing dev extension installation based on main (or older), then loading it with this branch, just to simulate an upgrade. I didn't change any values in storage for this branch, but I think it's good to confirm the logic in place is correct for all existing accounts! That's a good practice for any Keychain update.

We want to make sure that the viewing key (and default address) we derived from a mnemonic matches what is imported when we import the spending key directly. Also, and most critically, we need to ensure that this works with previous extension data in place, and doesn't affect the normal account flows in any way!

Since the PR introduces "Access Spending Key", we can test with any mnemonic import:

1. Import mnemonic
2. In Keychain popup -> View Keys -> Access Spending Key - copy this value and make note of Viewing key and payment address (default address)
3. Delete this account from keychain (avoiding duplicates)
4. Import Spending Key
5. Verify that Viewing Key & Payment address are the same (since we are using deterministic payment addresses for now)

Testing accounts

Here are a few accounts we can test with:

Mnemonic code: equip will roof matter pink blind book anxiety banner elbow sun young

• Using HD derivation path m/32'/877'/0'
  • Viewing key: zvknam1q080khy2qqqqpqp3qmymr4d28kgmwy0frpv89csgpd0azueh2deuu6t97cztywgh3mgkp4zhvjfxy2zjuk6y7j5w45f2mk94cnd4kqsndjtp6e7ezv59rm8czavrwjpw0dqtmmq6lrfnvrj57qspy2vlrv7gkmw3zktr5yyplmmp5hsf3reqnnuyfdt30zpkxzjdkq9t3d79z2cwx7y99dtdtrr48n9q7wphhwqxg9lxnass4njj6v09j48atd49kfj589ej5rk0gpswcm8qf
  • Spending key: zsknam1q080khy2qqqqpqp3qmymr4d28kgmwy0frpv89csgpd0azueh2deuu6t97cztywgh36uz5vhuw5wg5en4vlprudwkshg9t435c9stne4dvt64n02z2susqewexquafzcsplgd37d5wzta4ypmfamx43vxsde2p63r2y34xngflmmp5hsf3reqnnuyfdt30zpkxzjdkq9t3d79z2cwx7y99dtdtrr48n9q7wphhwqxg9lxnass4njj6v09j48atd49kfj589ej5rk0gpsc8tuen
• Using HD derivation path m/32'/877'/1'
  • Viewing key: zvknam1q080khy2qyqqpqr5w2asdwt4knzw92c5zenpz0ccj2f6m8u4t670wgja23hh38xwc07qjt96pze42mhyw3wrxglj2anjwffafl3ggkuutpwde7rftp7ekkzdznm577wdrkheacgglrqpfasnyw7ecknqpqzzcack0ng6vny33nt7z0hyw647g8gw9sr2585732d7cnfvmvkwqsd3efw96haa4k2pnmfmyh2rf9uknstm6dzwe97nkqw3nxltzj9pwrm06zmzqxlwt3g45ts0e
  • Spending key: zsknam1q080khy2qyqqpqr5w2asdwt4knzw92c5zenpz0ccj2f6m8u4t670wgja23hh38xwcw08c7cp64hauuf8uv44d3uy4gh6zwr9c6cegsy66exmgah2rlqseydkzl5rydtz3sr6dtm0yxhd4eagmre8vjrpyppzjpcm98ynx6gz3nt7z0hyw647g8gw9sr2585732d7cnfvmvkwqsd3efw96haa4k2pnmfmyh2rf9uknstm6dzwe97nkqw3nxltzj9pwrm06zmzqxlwt3g47ty63
• Using HD derivation path m/32'/877'/2'
  • Viewing key: zvknam1q080khy2qgqqpqrp6vhyc2d39vpn5rty473yzycelycdlmlzxkj6jyevtw4x4ycm2jujg3463hx2nlgwuw45yfgl2dr86te7u4t4s6p57fzuvsxmkumk8mwpafv8cfdqcalrt9h2vngqag3q2hae0mp6ptv3zdgyjh0ycv38j07f0ckn9mkszd4kc6t3lpn37engast5lct67ef6dg3uezqzmxpmps43xlvgfjkxhlhd07k8c5klqhl0ymxpk0wlvr22wnshnqvuc0crg6tme
  • Spending key: zsknam1q080khy2qgqqpqrp6vhyc2d39vpn5rty473yzycelycdlmlzxkj6jyevtw4x4ycm2smstj8dh97jssumgnz6zx9me40fz4yvfgv26jp20anf0yct2p3smjaqtydk6zd3u96c5v4y95e4dplygxzywn8m8nknfu52kjcf6lqgj07f0ckn9mkszd4kc6t3lpn37engast5lct67ef6dg3uezqzmxpmps43xlvgfjkxhlhd07k8c5klqhl0ymxpk0wlvr22wnshnqvuc0cd753f6

Screenshots

Spending Key auth prompt:

Spending Key view (Pending final copy):

Button appears before Viewing Key and should only display on non-Ledger shielded accounts:

Spending Key Import - New Tab:

[mateuszjasiuk]

Tested! LGTM