Pass advances to Minikin for calculating getTextRunCursor

Previously, the getTextRunCursor() implementation in Minikin ignored
the font and just used the characters in the buffer in order to
determine cursor positions. Now we calculate the advances beforehand
in order to find potential Indic clusters.

Test: Manually tested some Tamil sequences
Bug: 35721792
Change-Id: I2500bd4c2c9d07bb6c965b2d41e04853886a7391