Check package name format before using it for SPA nav

Bug: b/372895305
Test: unit test
Flag: EXEMPT bug fix
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:b2ee5ccf5b79d50cf53a86716042f0e2d7ff42ad)
Merged-In: Ife615c78c48a2d6f5b938c880c9c2128c5551644
Change-Id: Ife615c78c48a2d6f5b938c880c9c2128c5551644
2 files changed