[ProfileSummary] Add partial profile annotation on IR.

[ProfileSummary] Add partial profile annotation on IR.

Profile and profile summary are usually read only once and then annotated
on IR. The profile summary metadata on IR should include the value of the
newly added partial profile flag, so that compilation phase like thinlto
postlink can get the full set of profile information.

Differential Revision: https://reviews.llvm.org/D78310