perf(token): Speed up `take_until` under simd

[epage]

This reverts commit 489aa2ace0ce77790cf8d2aa3fc0fcf8a8f7ccb2.

PR #86 "FindSubstring<&[u8]>: make use of memchr::memmem"

When testing under gitoxide, it turned out this slowed down gitoxide-specific micro-benchmarks from ~170ns to ~240ns

[epage]

Important to note that for gitoxide, take_until looks for

• space
• newline
• :
• >
• <
• PGP signature begin
• PGP signature end

So its a mix of single-character (the memchr shortcut) and actual substring search