bidiFlags != SkPaint::Flags

We've a number of native functions in the text layout path that take
a bidiFlags argument. We've a number of callers of those functions
passing in SkPaint::Flags in that slot. This completely breaks text
directionality for the affected functions, as
SkPaint::kAntiAlias_Flag happens to share values with kBidi_RTL,
resulting in anti-aliased SkPaints measuring text as if it were RTL,
and non-anti-aliased SkPaints measuring text as if it were LTR,
regardless of the actual text directionality. Oops!

To address the issue, this commit replaces erroneous calls to
SkPaint.getFlags() with the value of Paint.mBidiFlags, and includes
the necessary plumbing to get that value where it needs to be.

Bug: 8471481
Change-Id: I2d04b70defed3130fc1ad13f4c9098f5fce4ffde