[roll] Roll fuchsia [wlancfg][telemetry] Optimize test time advancement

Optimize `TestHelper::advance_by` to dynamically jump to the next
scheduled timer's deadline (using `fasync::TestExecutor::next_timer`)
instead of advancing in fixed 1-second increments.

For tests that wait for large virtual durations (like 5 days in
`test_stat_cycles`), this reduces the number of iterations from
432,000 to ~28,800 (or fewer), drastically reducing CPU overhead
and preventing timeout flakes on slow emulated builders.

Also add an initial poll step at the current virtual time (before the
first jump) to ensure that any pending events sent just before the
call are processed at their correct virtual arrival time, preventing
functional failures in other tests.

Remove the now-unused `STEP_INCREMENT` constant.

Original-Original-Bug: 515847522
Test: fx test wlancfg-tests

TAG=agy
CONV=79221bfd-2df4-4c74-9fe4-d363712856c6

Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1627394
Original-Original-Revision: 096162cf6bfff4536cd91a22251e25272ae84000
GitOrigin-RevId: cf5e9fdfca660221354a83588850113aaf7a4cf6
Change-Id: I4ebcc3f8323286222f2f066ea95dda250e71976e
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1626939
Cr-Commit-Position: refs/heads/main@{#193468}