Define new fill request flag to indicate reqeust is for pcc. Have assist

structure set the AUTOFILL_INCLUDE_NOT_IMPORTANT_VIEW flag when pcc
request flag is set.
In this way, assist structure generated for PCC would have unimportant
views included

Bug: b/254877316

Test: Verified locally unimportant views are included in assist
structure by manually setting the fill request flag in
Session#requestAssistStructureLocked()

Change-Id: I75f8af9fbad6d3d19b5fe912a83b4685f1bb1ae5