Auto merge of #157234 - Walnut356:test_package, r=jieyouxu

Convert `lldb_batchmode` to a package

The new testing logic for https://github.com/rust-lang/rust/issues/148483 will end up being a couple of python files, and it doesn't make sense to have them all as freefloating scripts in `src/etc`. 

I also made sure to update occurrences of `lldb_batchmode.py` in the code and documentation to point to the new package instead.