Delegate libtest to the testing-devex team

[Amanieu]

The library team has not had much involvement in the development of libtest. Its API is entirely unstable and the only user-visible part is the argument parsing and environment variables. Given the work towards supporting alternative test harnesses, we would like to delegate all decision-making power over the API of libtest to the testing-devex team.

Practically speaking this means that API changes to libtest will only require an FCP from the testing-devex team and not libs-api.

cc @rust-lang/testing-devex @rust-lang/libs @rust-lang/libs-api

[Amanieu]

@rfcbot merge

[rfcbot]

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @cuviper
• @joshtriplett
• @m-ou-se
• @the8472
• @thomcc

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

psst @Amanieu, I wasn't able to add the final-comment-period label, please do so.