[Indic] Fix Khmer syllable-final coeng-consonant

[Indic] Fix Khmer syllable-final coeng-consonant

Brings down Khmer failures from 162 to 47.

KHMER: 299077 out of 299124 tests passed. 47 failed (0.0157125%)

Also rebaselined some of the test files that had only-inherited lines.
Removing those, the stats are:

BENGALI: 353893 out of 354188 tests passed. 295 failed (0.0832891%)
DEVANAGARI: 707315 out of 707394 tests passed. 79 failed (0.0111678%)
GUJARATI: 366438 out of 366457 tests passed. 19 failed (0.00518478%)
GURMUKHI: 60704 out of 60747 tests passed. 43 failed (0.0707854%)
KANNADA: 951042 out of 951913 tests passed. 871 failed (0.0915%)
KHMER: 299077 out of 299124 tests passed. 47 failed (0.0157125%)
LAO: 53611 out of 53644 tests passed. 33 failed (0.0615167%)
MALAYALAM: 1047994 out of 1048334 tests passed. 340 failed (0.0324324%)
ORIYA: 42320 out of 42329 tests passed. 9 failed (0.021262%)
SINHALA: 271666 out of 271847 tests passed. 181 failed (0.0665816%)
TAMIL: 1091754 out of 1091754 tests passed. 0 failed (0%)
TELUGU: 970553 out of 970573 tests passed. 20 failed (0.00206064%)
TIBETAN: 208469 out of 208469 tests passed. 0 failed (0%)

Still some regressions, but some of the more egregious cases are
addressed.