benchmark, libs: remove needless RegExp capturing

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

benchmark, readline, repl, url, util

Use non-capturing grouping or remove capturing completely when:

• capturing is useless per se, e.g. in test() check;
• captured groups are not used afterward at all;
• some of the later captured groups are not used afterward.