chore: organize KeyringRpcMethod enum by category

[danroc]

The KeyringRpcMethod enum lists RPC methods in an arbitrary order, making it harder to find related methods at a glance.

This PR reorganizes the enum entries into logical groups with comments:

• Account management
• Signing request management
• Account assets and transactions
• Dapp interaction

Examples

N/A - This is a code organization change with no functional impact.

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Note

Reorganizes KeyringRpcMethod into logical groups with comments to improve scanability.

• Groups methods under: Account management, Signing request management, Account assets and transactions, and Dapp interaction
• Only reorders enum entries and adds comments; no changes to method names, values, or logic

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