net/http.rb - fixup session timeout logic for OpenSSL 3

[MSP-Greg]

In OpenSSL 3, session.timeout may not allow negative values, although context.timeout can be negative. For more info see ruby/openssl#703.

Since the code here is using session.timeout in a non-standard way, use context.timeout. If it's nil, use session.timeout. This allows the code to work with OpenSSL 3.2.0.

[MSP-Greg]

I tested this locally without the two commits affecting the test.

In addition to this PR, commits 042faf7 & 58fc559 should be reverted, and PR #163 should be merged, which adds WIndows CI.

At present, the only simple way to test against OpenSSL 3.2.0 is to use a Windows Ruby master build, either head or ucrt.

[MSP-Greg]

I just rebased and additionally:
a) added Windows CI
b) removed the 'omit' in test_session_reuse_but_expire.

The branch is at https://github.com/MSP-Greg/net-http/commits/00-timeout-windows/, and CI passed.

Windows Ruby head builds all use OpenSSL 3.2.1, Ruby 3.2 and 3.3 are using OpenSSL 3.2.0.

[MSP-Greg]

Closing, see #178