[GSoC 2025] Templated Hooks - Weekly Update #4

[AlbertG]

This week I have worked on an 
[issue](https://github.com/dlang/dmd/pull/21483) that prevented 
my [`_d_interface_cast`](https://github.com/dlang/dmd/pull/21473) 
PR to run correctly in all scenarios. In short, the inlining for 
`CastExp` hasn't been set up right from the start, but somehow 
this was caught by the CI pipeline only now.

Moreover, I have begun the work on the templatization of 
`_adEq2`, which will be in fact replaced by the existing 
`__equals` function, with additional cleanups.