suppresses sign conversion warning in `TEMPLATE_PRODUCT_TEST_CASE`

[cjdb]

-Wsign-conversion was complaining about an implicit sign conversion, so this commit explicitly converts the unsigned type to a signed one.

Commit also adds a -Wsign-conversion to the list of warnings, and reorders that list so it's easier to spot what's missing (and removed two duplicate warnings).

Bug: #2348

Description

GitHub Issues

[cjdb]

Since this is a lot of work, I'm going to hold off on fixing this up any further till I get direction from a maintainer.

[horenmar]

Yeah, this is unmergeable like this.

If you want to pursue these changes, it will need to be merged in small pieces/commits, that are reviewable. e.g. I have no idea what actually changed in the template test registries (if anything) other than formatting.

A good way to start would be to cleanup the warnings + add sign conversions as no-error warning, so -Werror doesn't apply to it, then start merging fixups for reasonably small chunks. Also I prefer cleaning up type mixings when possible, rather than just adding casts everywhere. This is usually bit more work in the short term, but in the long term is easier to maintain.