[Meta] Bitcoin Support on Desktop

[yrliou]

What we have now:

• Creation of bitcoin accounts. Only Segwit(bc1...) accounts are supported now.
• Sending coins to addresses of types P2PKH, P2SH, P2WPKH, P2WSH and P2TR is supported
• Coin balance for account. We track set of used change and receive addresses for account and request balance for each of them from RPC.
• Account->Deposit generates first unused receive address for the account.
• Coin selections algorithm is adapted knapsack solver from BitcoinCore.
  • Groups utxos by address to spend them only together.
  • Sorts groups by total value.
  • Picks randomly starting from highest value group. Repeat this in many iterations.
  • Algorithm avoids dust outputs.
  • Algorithm uses adjust transaction fee by current fee rate.
• We use this api for RPC https://github.com/blockstream/esplora/blob/master/API.md
  • For testnet endpoint is Blockstream's public endpoint https://blockstream.info/testnet/api/
  • For mainnet endpoint would be brave proxy to chainstack node.
• When wallet is restored we run bitcoin account discovery(as for other coins) per bip-44

Scope of work:

• HDKey refactor and cleanup #27957
  HDKeyring refactoring #28270
  Bitcoin backend #29673
  Cleanup wallet code #30124
  KeyringService refactoring #30355
  Introduce AccountId mojo struct #30650
  Wallet's Keyring Id should be an enum instead of set of string constants. #30705
  Refactor WalletAccount in ui  #30851
  secp256k1_context instance should be global #31563
  Store derived account index in account's prefs #31537
  Refactor wallet SelectedAccount entity #31013
  Bitcoin account and networks in desktop ui #31565
  AccountId instead of address for transaction backend #31983
  Fix some circular deps in wallet's imports #32118
  AccountId instead of address for transaction frontends #32195
  blockstream.info as bitcoin testnet rpc endpoint #33000
  [Bitcoin] Fetch fee estimates and fee selector ui #32710
  [Bitcoin] Transactions frontend #32709
  [Bitcoin] Generate new change/receive address when needed #32716
  [Bitcoin] Bump bitcoin-core version #33513
  [Bitcoin] Support sending to different address types. #33648
  [Bitcoin] Account discovery on wallet restore #32717
  [Bitcoin] Need brave proxies for btc rpc endpoints #32726
  [Bitcoin] Support mainnet #32713
  Bitcoin feature flag for brave://flags #33866
  Bitcoin ui adjustments #34056
  Change BTC Mainnet explorer url to blockchain.com #34248
  [Bitcoin] Support custom network in settings page #32715
  Knapsack coin selection algorithm for bitcoin #34508
  bitcoin UTXO details should display the full address #34465
  max transfer isn't behaving as expected #34467
  Too many decimals issue when using "half" send button #34468
  Enable bitcoin feature by default for Nightly and Development channels #34731
  Backend should return BTC balance as total/pending/available tuple #34794
  TODO:
  [Bitcoin] Support legacy and taproot accounts #32712
  [Bitcoin] Imported and hardware accounts #32714
  [Bitcoin] Unittest coverage  #32718
  [Bitcoin] Error strings l10n #32719
  [Bitcoin] Support spending coinbase outputs #32720
  [Bitcoin] Android support #32721
  [Bitcoin] iOS support #32722
  [Bitcoin] P3A Support  #32723
  Add support for Bitcoin Dapps #34966
  Add support for Bitcoin Ordinals #34771

Related Security/Privacy reviews:

• https://github.com/brave/reviews/issues/1401
• https://github.com/brave/reviews/issues/1262
• https://github.com/brave/reviews/issues/1194
• https://github.com/brave/reviews/issues/1438

cc @jamesmudgett @bbondy @supermassive