Derive entropy choice update to Snaps API for Multi SRP

[ajeetd]

Requested by the Multi SRP team.

A recent SIP that the Multi SRP Team issued will mean a new feature will allow for multiple seed phrases in 1 wallet instance. This necessitates Snaps APIs to allow a user to “choose” where they derive entropy instead of defaulting to the first (only) seed.

SIP: MetaMask/SIPs#156

Feature narrative: https://docs.google.com/document/d/1EztNo7XOQEnQKHXk37K4rlXPfaWk1C_G2HDJJoKsPBw/edit?tab=t.0

[ajeetd]

Closing in favor of #2981