Fix max directionality in AndroidCharacter.getDirectionalities

U_CHAR_DIRECTION_COUNT has been used for boundary check for conversion
of directionality between ICU and Libcore.
However, the max directionality in ICU has been incresed from 18 to 22 since Unicode 6.3
https://github.com/unicode-org/icu/commit/2982958b06e#diff-c46912f650de1f607d39dd8d81fb4b57

But the max directionality has not been chagned in libcore, and thus it
will return undefined value in directionality_map.

Also, this commit also replaces @Deprecated API U_EA_COUNT
by u_getIntPropertyMaxValue(UCHAR_EAST_ASIAN_WIDTH).

Bug: 120073244
Bug: 117094880
Test: AndroidCharacterTest
Change-Id: I39918bdd4b06d0f1e95ad923594a28a0afc82b9e