Golang benchmark regex issues

[ml1nk]

The current regex for golang benchmark does not detect sub benchmarks (/ in name) and also does not works well when ns/op and MB/s are there at the same time.

goos: linux
goarch: amd64
pkg: github.com/uponusolutions/go-smtp/internal/textsmtp
cpu: AMD Ryzen AI 9 HX 370 w/ Radeon 890M
BenchmarkDotReader/Legacy-8         	      31	  43410346 ns/op	  96.62 MB/s
BenchmarkDotReader/Optimized-8      	      28	  43191982 ns/op	  97.11 MB/s
BenchmarkDotWriter/Legacy-8         	       1	2360375760 ns/op	 113.73 MB/s
BenchmarkDotWriter/Optimized-8      	      10	 105365395 ns/op	2547.66 MB/s