This fixes 2 issues:
- we used to index `adjusted_global_expressions` with the handle index of the constant instead of its initializer
- we used to adjust the initializer multiple times if the arena contained multiple `Expression::Constant`s pointing to the same constant
Allow `LocalVariable::init` to be an override expression.
Note that this is unrelated to WGSL compliance. The WGSL front end
already accepts any sort of expression as an initializer for
`LocalVariable`s, but initialization by an override expression was
handled in the same way as initialization by a runtime expression, via
an explicit `Store` statement.
This commit merely lets us skip the `Store` when the initializer is an
override expression, producing slightly cleaner output in some cases.
* add GL_EXT_texture_shadow_lod feature detection
* allow more cases of cube depth texture sampling in glsl
* add test for sampling a cubemap array depth texture with lod
* add test for chosing GL_EXT_texture_shadow_lod over the grad workaround if instructed
* add changelog entry for GL_EXT_texture_shadow_lod
* fix criteria for requiring and using TEXTURE_SHADOW_LOD
* require gles 320 for textureSampling over cubeArrayShadow
* prevent false positives in TEXTURE_SHADOW_LOD in checks
* make workaround_lod_with_grad usecase selection less context dependant
* move 3d array texture error into the validator
* correct ImageSample logic errors
