test: Fix environment-dependent flaky assertion in TestTraceInfoOnTimeoutWithSetTimeout

[Yashh56]

close #1166

PR Description

What does this PR do?
Fixes an environment-dependent assertion in TestTraceInfoOnTimeoutWithSetTimeout/timeout_with_very_short_timeout that causes the test suite to fail when run in a network-isolated environment (e.g., docker --network none).

Why is this change necessary?
The test previously asserted assertTrue(t, tr.DNSLookup == 0) under the assumption that a request with an extremely short timeout (1ms) will consistently abort and time out while waiting for DNS resolution. However, in an offline or heavily isolated environment, DNS resolution instantly fails via network-level errors (like connection refused) well before the timeout limit is reached. This records a microscopic but non-zero duration for tr.DNSLookup, causing the strict == 0 assertion to fail.

How does it work?
This PR updates the strict tr.DNSLookup == 0 check to a stronger, mathematically sound, and environment-agnostic invariant:

assertTrue(t, tr.DNSLookup <= tr.TotalTime)

This guarantees that the measured DNS phase duration logically fits within the overall bound of the request's total time—regardless of whether DNS failed instantly or if the context organically timed out.

The subsequent assertions (ConnTime == 0, TLSHandshake == 0, TCPConnTime == 0, ServerTime == 0) remain completely unchanged. This preserves the original and primary intent of the test: ensuring that a request aborting early never successfully progresses to establishing a network connection.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.73%. Comparing base (c874c8a) to head (3e76ab4).

Additional details and impacted files

@@           Coverage Diff           @@
##               v3    #1184   +/-   ##
=======================================
  Coverage   99.73%   99.73%           
=======================================
  Files          20       20           
  Lines        4141     4141           
=======================================
  Hits         4130     4130           
  Misses          7        7           
  Partials        4        4           

Flag	Coverage Δ
unittests	99.73% <ø> (ø)

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