clippy: Fix redundant_* warnings

[eerii]

Fixes redundant_* clippy warnings. Also updates the spec comments in the files changed to be propper rustdoc.

• redundant_file_names: Removes duplicate field names in struct initialization to avoid.
• redundant_closure: Functions can be passed directly instead of wrapping them in a closure.
• redundant_pattern_matching: is_ok and is_err can be used instead. Here the only part I'm unsure is what to do about the steps in components/script/dom/url.rs, since this merges step 2.2 and 3 together.
• redundant_guards: The pattern can be added directly to the Some(...) pattern instead of checked with an extra if.

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• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes are a part of Fix as many clippy problems as possible #31500
• These changes do not require tests because they don't modify behaviour

[jdm]

Thanks!