connect_attempts AuTest is flaky: the gold file pins sm_id, which is ordering dependent

[bryancall]

Summary

connect_attempts fails intermittently. The gold file pins the HTTP state machine id
of each transaction, which is an ordering artifact rather than part of the behaviour
the test is asserting.

Observed

CI build 43249, AuTest 0of4, 1 failed out of 146 tests. Every other assertion in the
run passed; the failure is a gold diff:

- ... for host='example.com' sm_id=0 ... retry_attempts=0 ...      (gold)
+ ... for host='example.com' sm_id=2 ... retry_attempts=0 ...      (actual)

- ... url='...' fail_count='3' marking down                        (gold)
+ ... url='...' fail_count='2' marking down                        (actual)

Retriggering the identical commit passed, so it is not deterministic.

Cause

tests/gold_tests/dns/gold/connect_attempts_single_max_retries_error_log.gold
wildcards the timestamp and the port on every line, but spells the state machine id
out literally:

`` CONNECT: attempt fail [CONNECTION_ERROR] to 0.0.0.1:`` for host='example.com' sm_id=0 `` retry_attempts=0 url='...'
`` CONNECT: attempt fail [CONNECTION_ERROR] to 0.0.0.1:`` for host='example.com' sm_id=2 `` retry_attempts=0 url='...'

The test drives two transactions. The gold assumes the one that gets sm_id=0 always
logs its retries before the one that gets sm_id=2. When the two interleave the other
way the comparison fails, even though the retry behaviour under test was correct.

fail_count has the same character: it is a counter sampled at a moment, not the
property the test exists to check.

Testers.GoldFile compares line by line and has no ordering option, so the gold itself
is where this has to be addressed.

Suggested fix

Wildcard the state machine id the same way the timestamp and port already are, so the
gold asserts what the test is about (two transactions, each retried the configured
number of times) rather than which id they were assigned. If the count of distinct
transactions matters, that is better expressed as a separate assertion than by pinning
the ids.

If preserving the ids is deliberate, Testers.GoldFileList accepts several golds and
passes on any of them, which would cover both interleavings.

Notes

Found while testing an unrelated change, #13661, whose diff is limited to
src/tsutil/Regex.cc, its unit test, and the regex_remap autest. connect_attempts
does not use regex, and the test passed five out of five locally on that branch.

Same class as #13662: a test asserting an incidental runtime value.