Properly set CharsetGroupProber.state to FOUND_IT

[dan-blanchard]

Throughout the rest of the chardet code we assume that FOUND_IT means we can stop looking. Previously the CharsetGroupProber did not set its state appropriately when a child prober returned FOUND_IT. This substantially speeds up the chardet for most encodings.

Fixes #202

Before change:

Benchmarking chardet 4.0.0 on CPython 3.7.5 (default, Sep  8 2020, 12:19:42)
[Clang 11.0.3 (clang-1103.0.32.62)]
--------------------------------------------------------------------------------
.......................................................................................................................................................................................................................................................................................................................................................................
Calls per second for each encoding:
ascii: 32887.903815995815
big5: 3.906468756080019
cp932: 2.980933994770643
cp949: 1.7553914946606737
euc-jp: 2.7375734716114426
euc-kr: 2.948884082793895
euc-tw: 67.4964556469068
gb2312: 4.909248428000002
ibm855: 15.664702233398641
ibm866: 35.52791448770514
iso-2022-jp: 1916.0822293284605
iso-2022-kr: 16663.901470003973
iso-8859-1: 65.22453585573267
iso-8859-5: 24.604965867422464
iso-8859-7: 39.346294718222524
koi8-r: 28.07679900564193
maccyrillic: 21.481341737898905
shift_jis: 4.096676458365973
tis-620: 9.342617557947577
utf-16: 93518.48383500558
utf-32: 82727.88954635109
utf-8: 23.69032943598593
utf-8-sig: 94042.69058295964
windows-1251: 25.231271611701636
windows-1252: 212.92666644668208
windows-1255: 13.980774444448262

Total time: 503.4055278301239s (7.131427450696289 calls per second)

After change

Benchmarking chardet 4.0.0 on CPython 3.7.5 (default, Sep  8 2020, 12:19:42)
[Clang 11.0.3 (clang-1103.0.32.62)]
--------------------------------------------------------------------------------
.......................................................................................................................................................................................................................................................................................................................................................................
Calls per second for each encoding:
ascii: 38176.31067961165
big5: 12.86915132656389
cp932: 4.656400877065864
cp949: 7.282976434315926
euc-jp: 4.329381447610525
euc-kr: 8.16386823884839
euc-tw: 90.230745070368
gb2312: 14.248865889128146
ibm855: 33.30225548069821
ibm866: 44.181691968506
iso-2022-jp: 3024.2295767539117
iso-2022-kr: 25055.57945041816
iso-8859-1: 59.25262902122995
iso-8859-5: 39.7069713674529
iso-8859-7: 61.008422013862194
koi8-r: 41.21560517643845
maccyrillic: 31.402474369805002
shift_jis: 4.9091652743515155
tis-620: 14.408875278821073
utf-16: 177349.00634249471
utf-32: 186413.51111111112
utf-8: 108.62174360115105
utf-8-sig: 181965.46637744035
windows-1251: 43.16933400329809
windows-1252: 211.27653358317968
windows-1255: 16.15113643694104

Total time: 268.0230791568756s (13.394368915143872 calls per second)

Futhermore, this finally makes chardet 4.x faster than 3.x, which was one of the main things holding up its release.

3.0.4 benchmarks for reference:

Benchmarking chardet 3.0.4 on CPython 3.7.5 (default, Sep  8 2020, 12:19:42)
[Clang 11.0.3 (clang-1103.0.32.62)]
--------------------------------------------------------------------------------
.......................................................................................................................................................................................................................................................................................................................................................................
Calls per second for each encoding:
ascii: 25559.439366240098
big5: 7.187002209518091 X
cp932: 4.71090956645177 X
cp949: 2.937256786994428 X
euc-jp: 4.870580412090848 X
euc-kr: 6.6910755971933416 X
euc-tw: 87.71098043480079 X
gb2312: 6.614302607154443 X
ibm855: 27.595893549680685 X
ibm866: 29.93483661732791
iso-2022-jp: 3379.5052775763434 X
iso-2022-kr: 26181.67290886392 X
iso-8859-1: 120.63424740403983 X
iso-8859-5: 32.65106262196898 X
iso-8859-7: 62.480089080556084 X
koi8-r: 13.72481001727257
maccyrillic: 33.018537255804496 X
shift_jis: 4.996013583677438 X
tis-620: 14.323112928341818 X
utf-16: 166771.53081510935 X
utf-32: 198782.18009478672 X
utf-8: 13.966236809766901 X
utf-8-sig: 193732.28637413395 X
windows-1251: 23.038910006925768
windows-1252: 99.48409117053738
windows-1255: 6.336261495718825

Total time: 357.05358052253723s (10.054513372323958 calls per second)