Calculate the number of out vregs.

Determine the number of out vregs needed by invokes that
actually make a call, and by `HStringBuilderAppend`s.
This can yield smaller frame sizes of compiled methods when
some calls are inlined or fully intrinsified.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 358519867
Change-Id: I4930a9bd811b1de14658f5ef44e65eadea6a7961