refactor: move validation structs and add account field

[Battambang]

Explanation

This PR contributes to supporting the Bitcoin dApp connectivity.
It's refactoring the current code to prepare the integration of the resolve account address Keyring method.

It is part from the initial PR #564 feat: enable account address resolution to support dApps connectivity to split the work into 3 smaller PRs:
#589 refactor: move validation structs and add account field
#590 feat: add resolveAccountAddress method to KeyringHandler for dApp connectivity routing
#591 feat: add confirmation dialog before sendTransfer and before signing a PSBT from the keyring handler

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

---

Note

Medium Risk
Medium risk because it changes the validated shape of keyring request params (adds required account.address and method-specific structs), which can break callers if they haven’t been updated; logic changes are mostly limited to validation and tests.

Overview
Refactors Bitcoin keyring request validation by moving the request superstruct schemas out of KeyringRequestHandler into handlers/validation.ts and introducing method-specific keyring request structs (via BtcMethod literals) plus a shared WalletAccountStruct.

Updates request shapes so Bitcoin capability calls now validate a required params.account.address field for actions like SignPsbt, FillPsbt, ComputeFee, BroadcastPsbt, SendTransfer, GetUtxo, and SignMessage, with unit/integration tests adjusted accordingly. Also adds NetworkStruct in caip.ts and bumps the snap manifest bundle shasum.

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[Battambang]

@metamaskbot publish-preview

[github-actions]

Preview builds have been published. See these instructions for more information about preview builds.

Expand for full list of packages and versions.

{
  "@metamask-previews/bitcoin-wallet-snap": "1.10.0-preview-bee05b0"
}

[Battambang]

@metamaskbot publish-preview

[github-actions]

Preview builds have been published. See these instructions for more information about preview builds.

Expand for full list of packages and versions.

{
  "@metamask-previews/bitcoin-wallet-snap": "1.10.1-preview-2c3d8f3"
}