Lower default SSL peek test rounds and remove CI workarounds

[justsmth]

Issues:

Resolves #3141

Description of changes:

The SSL runner's DEFAULT_PEEK_ROUNDS of 50 has been causing i/o timeouts on non-Linux platforms for a while now. We've been working around this by setting AWS_LC_SSL_TEST_RUNNER_PEEK_ROUNDS=5 in CI for Windows, OpenBSD, FreeBSD, and NetBSD — but that leaves anyone building locally on those platforms hitting the same failures (#3141).

This lowers the default from 50 to 5 and removes all the per-job CI overrides. The sanity-test-run job (Linux, ubuntu-latest) now runs with AWS_LC_SSL_TEST_RUNNER_PEEK_ROUNDS=100 to provide stress-test coverage of the peek buffer drain/refill cycle on a platform that can comfortably handle it.

Call-outs:

The peek test verifies the SSL_peek → SSL_peek → SSL_read state transition per TLS record. Each round exercises the same code path — the internal buffer fill/drain cycle through ssl->s3->pending_app_data. 5 rounds is sufficient for correctness; higher round counts only repeat the same transition and don't exercise additional code paths. The env var override remains available for targeted stress testing.

The AWS_LC_SSL_TEST_RUNNER_PEEK_ROUNDS env var support in runner.go and the AWS_LC_SSL_RUNNER_IDLE_TIMEOUT CMake plumbing are intentionally preserved as general-purpose knobs for slow environments or stress testing.

Testing:

CI should pass without the per-platform peek rounds overrides. The FreeBSD, OpenBSD, NetBSD, and Windows jobs are the ones to watch. The sanity-test-run job validates the stress-test configuration at 100 rounds on Linux.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.93%. Comparing base (401a31b) to head (2ea8a40).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3155      +/-   ##
==========================================
- Coverage   77.95%   77.93%   -0.02%     
==========================================
  Files         689      689              
  Lines      122537   122537              
  Branches    17071    17070       -1     
==========================================
- Hits        95526    95503      -23     
- Misses      26112    26136      +24     
+ Partials      899      898       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[dougch]

nit; the comment on https://github.com/aws/aws-lc/blob/main/CMakeLists.txt#L1342 needs an update.