Improve language detection performance

[aleks-p]

Closes #2777

1. If the profile has the pyroscope_spy label, we use it to determine the language
2. If we do need to look into the string table, we use prefix and suffix matching instead of regular expressions

Here is a summary of the gains with 2:

Regexp:

go.cpu.labels.pprof-10         	  330040	     10853 ns/op
heap-10                        	  195819	     18407 ns/op
dotnet.labels.pprof-10         	  143966	     24949 ns/op
profile_java-10                	   61840	     58016 ns/op
profile_nodejs-10              	  109437	     32871 ns/op
profile_python-10              	  391418	      9156 ns/op
profile_ruby-10                	  307896	     11783 ns/op
profile_rust-10                	  636633	      5668 ns/op

String matching (prefix or suffix):

go.cpu.labels.pprof-10         	 3418387	      1060 ns/op
heap-10                        	 2446440	      1483 ns/op
dotnet.labels.pprof-10         	 1751536	      2057 ns/op
profile_java-10                	 2333244	      1541 ns/op
profile_nodejs-10              	 1722144	      2083 ns/op
profile_python-10              	 4395427	       821 ns/op
profile_ruby-10                	 4546932	       793 ns/op
profile_rust-10                	 2960469	      1221 ns/op

benchstat:

goos: darwin
goarch: arm64
pkg: github.com/grafana/pyroscope/pkg/pprof
                                                    │    old.txt    │               new.txt               │
                                                    │    sec/op     │   sec/op     vs base                │
_GetProfileLanguage/testdata/go.cpu.labels.pprof-10    10.589µ ± 0%   1.016µ ± 0%  -90.40% (p=0.000 n=10)
_GetProfileLanguage/testdata/heap-10                   18.034µ ± 1%   1.411µ ± 0%  -92.18% (p=0.000 n=10)
_GetProfileLanguage/testdata/dotnet.labels.pprof-10    24.765µ ± 1%   1.981µ ± 1%  -92.00% (p=0.000 n=10)
_GetProfileLanguage/testdata/profile_java-10           57.873µ ± 1%   1.473µ ± 0%  -97.46% (p=0.000 n=10)
_GetProfileLanguage/testdata/profile_nodejs-10         32.770µ ± 0%   2.010µ ± 1%  -93.87% (p=0.000 n=10)
_GetProfileLanguage/testdata/profile_python-10         9125.0n ± 1%   790.8n ± 0%  -91.33% (p=0.000 n=10)
_GetProfileLanguage/testdata/profile_ruby-10          11754.5n ± 1%   772.7n ± 1%  -93.43% (p=0.000 n=10)
_GetProfileLanguage/testdata/profile_rust-10            5.679µ ± 1%   1.184µ ± 0%  -79.16% (p=0.000 n=10)
geomean                                                 16.49µ        1.253µ       -92.40%

As before, there is a chance of false detection - though this is only used for statistics for now.

[korniltsev]

There may or may be not a new spy label from grafana agent pyroscope.java component

https://github.com/grafana/agent/pull/5985/files#diff-a0c3d4195b76376947e1f9e0059dc3538e97c3fb10ba70d9000ea74b902c1f8dR244

Let me know if you have any preference for its value or its presence

[aleks-p]

Thanks @korniltsev, the value makes sense to me. I'll add the mapping for it.