Fix a few clippy lints in libtest

[jyn514]

• Remove unnecessary references and dereferences
• Use .contains instead of a <= x && x <= b
• Use mem::take instead of mem::replace where possible

cc #106394 :)

[rustbot]

r? @thomcc

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[jyn514]

@bors rollup

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[kadiwa4]

Clippy should ideally suggest methods like char::is_ascii_uppercase for those letter ranges

[jyn514]

ah good point - I can switch to using those APIs in libtest

[thomcc]

These look fine to me.

@bors r+

[bors]

📌 Commit 3534e0a has been approved by thomcc

It is now in the queue for this repository.