GL_HALF_FLOAT_OES and GL_HALF_FLOAT have different enum values, and we
weren't handling the case where a half-float texture was already
created (e.g. with an effective internal format of GL_RGBA16F) and then
updated with a glTexSubImage call using GL_HALF_FLOAT_OES type. In
other words, we assumed the OpenGL ES 3.0 sized internal format could
only be used with the OpenGL ES 3.0 half-float type, but this hasn't
been true since we started storing only the effective internal format
for all versions.

Note that GL_OES_texture_half_float, which defines GL_HALF_FLOAT_OES,
does not clarify whether HALF_FLOAT images can be updated using FLOAT,
or vice-versa. We're assuming the equivalent combinations of OpenGL ES
3.0 table 3.3 are valid. That is, FLOAT can be used to update,
HALF_FLOAT, but not the other way around.

Bug b/74609191

Change-Id: Ib8548cd37065820eb59a0943fd39647edc5e9f1b
Reviewed-on: https://swiftshader-review.googlesource.com/17748Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>