feat(content): more ramp options

[chaosvolt]

Purpose of change

Another random item on the todo list, I was gonna add this to the mod but now it's mainlined so :3

Describe the solution

C++ changes:

1. In construction.cpp, defined versions of check_ramp_low and check_ramp_high that also call check_empty, so wooden ramps need clear space to construct on (unlike with the other two that construct on specific non-empty terrain).

JSON changes:

1. Added construction and construction group entries for rammed earth and wooden ramps. Each step is set to equal the resources needed to craft one rammed earth wall and wooden wall respectively. These currently, per feedback, produce generic ramps instead of specific terrain, since the ramp_up functions would all need to be special-cased in for each ramp type.
2. Edited name and description of road ramps to fit being used as generic ramps.

Describe alternatives you've considered

Figuring out how to JSONize the ramp functions properly.

Testing

1. Checked affected JSON files for syntax and lint errors.
2. Compiled and load-tested.
3. Constructed ramps with debug hammerspace on.
4. Confirmed that wooden ramps can't be built in shallow pits or fence posts like the other two are meant to.
5. Checked affected C++ file for astyle.

Additional context

Checklist

[scarf005]

i think until we get to make ramp generic on material it'd be better to not hardcode variants of it. (example: many many grills)

[chaosvolt]

So make the output generic instead of coding new ramp functions and adding new ramp terrain?

[scarf005]

yeah, i think it would be easier to maintain in the long term.

[scarf005]

the rules for building is quite confusing but at least i was able to build both two new types of ramps.