Replace MDX ModuleType with MDX SourceTransform (#8766)
### Description
Remove `ModuleType::Mdx` and instead handle mdx files using
```rust
ModuleRuleEffect::ModuleType(ModuleType::Typescript {
transforms: ts_app_transforms,
tsx: true,
analyze_types: enable_types,
options: ecmascript_options_vc,
}),
ModuleRuleEffect::SourceTransforms(Vc::cell(vec![Vc::upcast(
MdxTransform::new(mdx_transform_options),
)])),
```
### Testing Instructions
I ran these Next.js tests, which appear to be all mdx related tests
there are
```
mdx with-mdx-rs
app directory
✓ should work in initial html (1262 ms)
✓ should work using browser (1460 ms)
✓ should work in initial html with mdx import (145 ms)
✓ should work using browser with mdx import (1179 ms)
✓ should allow overriding components (1163 ms)
✓ should allow importing client components (26 ms)
✓ should work with next/image (424 ms)
pages directory
✓ should work in initial html (1091 ms)
✓ should work using browser (1216 ms)
✓ should work in initial html with mdx import (147 ms)
✓ should work using browser with mdx import (1202 ms)
✓ should allow overriding components (1236 ms)
```
