Made AutofillId.withoutSession is testable.

We add new test in stage-aosp-rvc-ts-dev for R2, we need make this API
testable.

Bug: 156408900
Test: atest android.autofillservice.cts.inline.\
InlineAugmentedWebViewActivityTest

Change-Id: I27d1227f858aac83b3de1cb8ef719edf177524dc
Merged-In: I27d1227f858aac83b3de1cb8ef719edf177524dc