Moving `#[cfg(test)]` modules into a separate files to save recompiling the `std` crate

[tesuji]

Proposal

Moving #[cfg(test)] modules into a separate files to save recompiling the std crate
when only that test file changes.

core and src/lib* crate already did that.

Moving tests around will be a very big change.
It also makes it harder to blame specific code in tests.
I would like infra member to take care of it, through I could do it myself if wanted.

Relevant PR:

• Avoid recompiling std when tests change in std::net rust#75108 cc @KodrAus

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Process

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• File an issue describing the proposal.
• A compiler team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
  • Finding a "second" suffices for internal changes. If however you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
  • Compiler team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
• Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

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Comments

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[rustbot]

This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

[petrochenkov]

@rustbot second

[tesuji]

Is this proposal accepted?