[Lacros] Add launch interface for Lacros app controller.

This CL adds the launch interface for Lacros crospi api to allow sending
launch command to Lacros to launch app.

BUG=1144877

Change-Id: I3cf70c16303094deddb2fb3f6158e573aaf8db08
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3121876
Commit-Queue: Maggie Cai <mxcai@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#917548}