[roll] Roll fuchsia [time] Stitches up fake time in timekeeping tests

Properly sets up fake executor clocks in unit tests to match the
system's mono and boot timelines.

Old code disregarded teh difference, causing some tests to be dependent
on how long the device running the test spent in suspend.

Also corrected some variable naming which was left over from when
Timekeeping was migrated to use the boot timeline.

Original-Bug: 404936065, 415115561
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1265835
Original-Revision: 0f29ae3fd230de9f2cbd2de08e0e6524773e5948
GitOrigin-RevId: 468214f09ed34e12edd4a75ca5eb487d34886743
Change-Id: I85c933154fd9c91d874f8e85b86476b96dbcc5cf

stem

diff --git a/stem b/stem
index b99ec14..8b04361 100644
--- a/stem
+++ b/stem
@@ -8,7 +8,7 @@
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-             revision="e99599e51a7ba5afd2213d757aa4ae9945866639"
+             revision="0f29ae3fd230de9f2cbd2de08e0e6524773e5948"
              />
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