ci(unit-tests): tshark apt install exceeds its 90s per-attempt bound on a slow mirror #1306

Describe the bug
Engines (PyShark) fails at "Install this engine's system packages" when the Azure Ubuntu mirror is slow. It has failed this way on #1225 (a docs-only PR), #1253 and #1287, so it is not caused by any PR's code.

Evidence (job 112943258387):

• Attempt 1: apt-get update exceeded its 45 s bound (18:17:51 → 18:18:36).
• Attempt 2: the update succeeded, but apt-get install tshark exceeded its 90 s bound while downloading libwireshark17t64 (23.7 MB, 18:19:21 → 18:20:12). The step then exits 1.

The bounds in unit-tests.yml:476-498 (engine-tests) and :743-756 assume a mirror that delivers about 1 MB/s. Today's mirror delivered roughly 0.5 MB/s.

Expected behavior
A slow but working mirror still completes the step. Raise the install bound to 180 s and the step cap to fit two attempts (45 s + 180 s, twice, is 450 s, so 8 min). A genuine hang still fails as a named step timeout, and the 30-minute job budget is untouched.