[native] add registerReservedWalletUser and registerReservedPasswordUser to CommRustModule

Summary:
pretty straightforward. just expose rust methods to js

Depends on D11908

Test Plan: tested from js later in stack by calling the useLogIn hook with a reserved username and reserved wallet address and confirming that i was registered on identity

Reviewers: bartek, kamil

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11909