[iOS][Mojo] Enhanced calendar mojo interface and service, menu hook up

Mojo interface for enhanced calendar, its service implementation, and
the service being used in the AI prototyping menu. This interface takes
in a proto wrapper, and also outputs a proto wrapper or an MES
error string if there is one. Users of this service presumably wouldn't
simply want a string representation of the response proto, so they
receive the proto itself, or the error string if there isn't a response
proto.

Bug: 390621435
Change-Id: I5fcd651359802ad893fa214673affa086acaa242
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6297885
Reviewed-by: Adam Arcaro <adamta@google.com>
Commit-Queue: Nicolas MacBeth <nicolasmacbeth@google.com>
Reviewed-by: Giovanni Ortuno Urquidi <ortuno@chromium.org>
Auto-Submit: Nicolas MacBeth <nicolasmacbeth@google.com>
Reviewed-by: Joemer Ramos <joemerramos@google.com>
Cr-Commit-Position: refs/heads/main@{#1426515}