[GLUtils] Add support for GL_SRGB8_ALPHA8.

When a GL surface is configured as EGL_GL_COLORSPACE_SRGB_KHR, the pixel value
from fragment shader will be gamma-ed, to de-gamma the pixel value in fragment
shader, the texture uploaded through glTexImage2D needs to specify the internal
format as GL_SRGB8_ALPHA8. For backward compatibility, GLUtils should never
pick this internal format by itself, but it should allow developer to pass this
internal format if they really want to.

BUG: N/A
Test: Build, flash, boot and run my own test apk
Change-Id: Ic43c2f2e3533ebb41c1a85b33964c1f19ac74a7c