feat: add originMetadata to submitRequest

[FrederikBolding]

Description

Add an optional originMetadata field to submitRequest, which will be passed along in keyrings that are using at least platform version 12. This field can be used when using transports where the origin itself isn't verifiable.

https://consensyssoftware.atlassian.net/browse/WPC-1195

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Note

Medium Risk
Touches signing request routing and origin attribution across v1/v2 Snap keyrings; incorrect version gating could omit or leak metadata to incompatible Snaps, but behavior is covered by platform-version checks and tests.

Overview
Adds optional originMetadata on keyring submitRequest / KeyringRequest, with transport and selfReportedOrigin, so Snaps can reason about callers when the plain origin is not trustworthy (e.g. WalletConnect).

SnapKeyring and SnapKeyringV1 accept originMetadata and forward it only when the Snap platform is ≥ 12.0.0; older platforms get origin only (7.0.0–11.x) or neither field (< 7.0.0), via new toKeyringRequestWithoutOriginMetadata, submitRequestWithoutOriginMetadata, and updated toKeyringRequestWithoutOrigin (also strips originMetadata). EthKeyringV1Adapter always sends originMetadata: null on internal submits.

Coverage is extended across bridge, internal API, snap client, and v2 SnapKeyring paths.

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[ccharly]

LGTM!