Add optional parameter to IVsyncSource::vsyncDeadlineAfter

vsyncDeadlineAfter just forwards its parameter to
VSyncTracker::nextAnticipatedVSyncTimeFrom, but the latter has an
optional parameter, too. Adding the optional parameter to
vsyncDeadlineAfter allows Scheduler::getNextFrameInterval to call it
directly. This will further help to move getNextFrameInterval's impl
into FrameTargeter::beginFrame, in
I229e09ccd760341268423fd4ba1ecc5105186f10.

Use Android's TimePoint and related classes directly in
getNextFrameInterval.

Bug: 315371484
Test: atest libscheduler_test:SchedulerTest#nextFrameIntervalTest
Change-Id: I1ede36d692b82a1f7276071fa558decced743334
diff --git a/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp b/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
index a9abcaf..29711af 100644
--- a/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
+++ b/services/surfaceflinger/Scheduler/tests/FrameTargeterTest.cpp
@@ -38,7 +38,9 @@
     const TimePoint vsyncDeadline;
 
     Period period() const override { return vsyncPeriod; }
-    TimePoint vsyncDeadlineAfter(TimePoint) const override { return vsyncDeadline; }
+    TimePoint vsyncDeadlineAfter(TimePoint, ftl::Optional<TimePoint> = {}) const override {
+        return vsyncDeadline;
+    }
     Period minFramePeriod() const override { return framePeriod; }
 };