fix(gevent): unload time but not typing modules for module cloning

[Yun-Kim]

This PR makes a fix to #4863 which inadvertently removed unloading the time module as well as removing the typing module from the list of standard library modules to not unload for module cloning. We found that the time module is a special case (which is important to unload due to interactions with gevent patching) as it is implicitly imported by recent versions of CPython on interpreter startup, so it may be present in sys.modules already.
The typing module is also problematic on being reloaded for older versions of Python < 3.7, so we should not unload/reload this module as well.

Checklist

• Change(s) are motivated and described in the PR description.
• Testing strategy is described if automated tests are not included in the PR.
• Risk is outlined (performance impact, potential for breakage, maintainability, etc).
• Change is maintainable (easy to change, telemetry, documentation).
• Library release note guidelines are followed.
• Documentation is included (in-code, generated user docs, public corp docs).
• Author is aware of the performance implications of this PR as reported in the benchmarks PR comment.

Reviewer Checklist

• Title is accurate.
• No unnecessary changes are introduced.
• Description motivates each change.
• Avoids breaking API changes unless absolutely necessary.
• Testing strategy adequately addresses listed risk(s).
• Change is maintainable (easy to change, telemetry, documentation).
• Release note makes sense to a user of the library.
• Reviewer is aware of, and discussed the performance implications of this PR as reported in the benchmarks PR comment.

[emmettbutler]

@Yun-Kim would you mind editing the riotfile to show which additional versions of python this creates support for?

[P403n1x87]

Some nits, otherwise LGTM.

[pr-commenter]

Benchmarks

Comparing candidate commit 2564674 in PR branch yunkim/module-cloning-typing-time with baseline commit 6ff460e in branch 1.x.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 56 cases.

[Yun-Kim]

@Yun-Kim would you mind editing the riotfile to show which additional versions of python this creates support for?

Looks like this change still doesn't support Python versions <= 3.7 (Hangs on 2.7, see memalloc issues on Python 3 up until 3.8+). The likely fix to support the older Python versions is contained in #5105.