Add a new extension, ANGLE_get_tex_level_parameter which allows
users to query texture size and format information before ES 3.1.
This is very useful for re-using existing textures instead of
re-allocating.

Bug: chromium:1132514
Change-Id: I71f6bad8bdacb91875cc81b4884d4c3099235f3f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2469959Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>