Use idiomatic std::mem::take instead of std::mem::replace

[ShinysLove]

In several modules, we are resetting structures to their default values using std::mem::replace(&mut var, Default::default()). While this works, it is less idiomatic and more verbose than necessary.
Describe the solution you'd like
Replace these occurrences with std::mem::take(&mut var), which is the standard and more concise way to achieve the exact same behavior for types that implement Default.

Example

// Before
let old_value = std::mem::replace(&mut self.buffer, Vec::new());

// After
let old_value = std::mem::take(&mut self.buffer);

This change improves code readability and aligns with Rust best practices (clippy lint: mem_replace_with_default).

[rustbot]

Error: Unknown labels: A-code-quality

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[Morgane55440]

the only preexisting label i can see that would make sense here would be C-cleanup

[jieyouxu]

Mentoring instructions:

• Please don't spot-fix instances of this in the compiler. Instead, please enable clippy:: mem_replace_with_default on the compiler tree by adding it to

  rust/src/bootstrap/src/core/build_steps/clippy.rs

  Line 593 in 4f84d9f

  let compiler_clippy_cfg = LintConfig {

  , then fixing the instances in the compiler in a second commit.

For anyone wanting to claim / work on this: please refrain from fully LLM-generating a PR, E-easy issues are meant as learning opportunities for humans, especially new contributors. You can @rustbot claim this issue.

[JarlEvanson]

@rustbot claim

[backendsouls]

Running rg -r "std::mem::replace(&mut " . I got 54 occurrences, are we changing all of them regardless? If try this one as a first PR (hopefully from several) is there anything special I need to take carefully? Thank you!

Update: Did not saw the claim.