feat!: rename KeyringVersion to KeyringInternalFeature{,s}

[ccharly]

Replace KeyringVersion support to a feature-based variant.

This will allow to re-use a proper versioning of the keyring with the introduction of keyring capabilities.

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Note

Replaces version-based compatibility with explicit feature flags and updates legacy request handling across packages.

• Introduces KeyringInternalFeature (adds UseOrigin) and KeyringInternalFeatures; removes KeyringVersion
• Replaces platform mapping with PLATFORM_VERSION_TO_KEYRING_FEATURES and getKeyringFeaturesFromPlatform
• Renames v1 request types/methods to Legacy* (e.g., toLegacyKeyringRequest, LegacyKeyringRequest{,Struct}, LegacyKeyringResponse{,Struct}); updates exports to compatibility/legacy
• Renames client API submitRequestV1 to submitLegacyRequest and uses SubmitRequestResponseV1Struct
• Updates SnapKeyring to select submitRequest vs submitLegacyRequest based on UseOrigin; removes version-based submission path
• Updates tests and CHANGELOGs to reflect new feature-flag model and API renames

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