[BREAKING] Deprecate WebGL1 based texture sampling names with _EXT

[mvaligursky]

Marked as [BREAKING] as if the user code uses these macros in the shaders, they need to be renamed (EXT letters removed)

• the deprecated texture sampling are no longer an extension, but are core functionality, so rename the marcos
• keep old macros in a deprecated format to get useful shader compilation errors

See red lines with the old naming containing EXT, and green lines bellow with new names