feat: add KeyringVersion + KeyringCapabilites.versions

[ccharly]

Adding a new versions field in the capabilities.

This way, we will know what keyring API versions is supported and potentially adapt the requests we're sending to that keyring.

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Note

Introduces explicit keyring API versioning and updates implementations to declare support.

• Add KeyringVersion enum (V1, V2) and require non-empty versions in KeyringCapabilities (keyring-capabilities.ts)
• Update Ethereum keyring wrappers (hd-keyring-v2.ts, ledger-keyring-v2.ts, simple-keyring-v2.ts, trezor-keyring-v2.ts) to include versions: [KeyringVersion.V2]
• Adjust tests to provide versions in capabilities (keyring-wrapper.test.ts)
• Document changes in CHANGELOG.md

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[ccharly]

Closing this one as we might want to couple the new V2 change with a new Snap platform version. The long-term plan would be to incorporate the keyring API support within the platform itself, allowing us to benefit from a global versioning rather than a sub-version only for the keyring part.