[6.1] Cherry-pick two last-minute PRs

[QuietMisdreavus]

This PR cherry-picks two recent PRs that landed in main just after the release/6.1 branch was created.

cc @icanzilb @Kyome22

• Explanation: Refactors some code in the benchmark runner for performance and clarity.
• Scope: Small refactor; no change to behavior.
• Issues: Peak memory metric on Linux could be slightly more performant #1066
• Original PRs: Fix https://github.com/swiftlang/swift-docc/issues/1066 #1067
• Risk: Very low. The changed code is minor and has equivalent semantics.
• Testing: Automated and manual testing has passed.
• Reviewers: @d-ronnqvist

• Explanation: Updates Package.swift to use URLs ending in .git, for consistency with other first-party Swift packages.
• Scope: Minor update to package specification.
• Issues: None
• Original PRs: Fix the suffix of dependency urls in Package.swift #1073
• Risk: Very low. The change updates URLs to an equivalent URL that resolves to the same dependency.
• Testing: Automated testing has passed.
• Reviewers: @d-ronnqvist

[QuietMisdreavus]

@swift-ci Please test

[franklinsch]

@QuietMisdreavus do we still need this PR?

[QuietMisdreavus]

Yes. I was unfortunately OOO right when this was approved, and when i came back the branch was locked for the holiday. Thanks for the reminder; i'll merge this now.