Remove product debug files

These files are difficult to support in the Starlark product
configuration. They also aren't really a good representation
of products even with Makefiles, because they only display
information from products that have been imported with
import-nodes, but generate empty files for the other products
that are included from the imported ones.

For example, lunching aosp_arm64 then running
`m out/products/build/make/target/product/core_64_bit.mk.txt`
would generate a file full of empty variable assignments.

Bug: 221312856
Test: Presubmits
Change-Id: I18613a628968acc25b57b44e229de7df1b2476ef