Bazel: move patching of rules_kotlin to a registry override

[redsun82]

This would allow to share the patch with semmle-code without duplicating it, but as can be seen requires a lot of boilerplate, so I'm not entirely sure it's worth it.

[criemen]

I agree, if this is the only patch we'd need to share like this, it's not worth it.

[redsun82]

On the other hand, this might maybe avoid ql module sync dances down the line? Without this, we might need a semmle-code/codeql sync whenever we need to update rules_kotlin. With this, semmle-code can just have --registry=file://%workspace%/ql/misc/bazel/override_registry and not mention rules_kotlin at all. I'm a bit torn.

[redsun82]

I'm leaning more and more towards this solution because of the ease it gives with respect to semmle-code/codeql syncing (or rather lack thereof). To this end I've added a script that makes the whole process of managing this local registry much easier.

What do you think @criemen?