Update definition for "restricted" methods

[alexandratran]

We currently imply that a "restricted" method is a method that requires being passed directly to wallet_requestPermissions:

• https://docs.metamask.io/wallet/reference/json-rpc-api/
• https://docs.metamask.io/wallet/how-to/manage-permissions/
• https://docs.metamask.io/wallet/concepts/wallet-api/#restricted-methods

Under this definition, only eth_accounts is restricted. We want to modify this definition to include the signature, sending, and encryption methods that are enabled via eth_accounts.

Something along the lines of "restricted methods are methods that cannot be called unless you have permission to do so using wallet_requestPermissions or wallet_requestSnaps." Add a note to this definition stating that acquiring the eth_accounts permission includes/enables calling the restricted signing/sending methods.

Also include in the description of each restricted method how to acquire the permission (either via eth_requestAccounts or wallet_requestSnaps – this is already be done for the restricted Snaps methods).

See MetaMask/api-specs#195 for the full list of restricted methods.

[jiexi]

It would be great if we could loosen "restricted" enough to use it to describe permissioned snap methods as well

[vandan]

We'll need to specify that Snap methods that are restricted are a little different in that they need to go through wallet_requestSnaps rather than wallet_requestPermission for permissions.

[alexandratran]

Updated issue description.