Add helper functions to make tool usable n times

[Wuzzy2]

This adds two functions:

• item:add_wear_by_uses
• minetest.get_tool_wear_after_use

These are two helper functions for tools that have a specified number of uses before breaking. Two examples for such tools are MTG's Screwdriver and Flint and Steel. This makes sure the tool will break after the exact specified number of uses.

The first function actually adds the wear to the tool and (if neccessary) breaks it.
The second function only "simulates" it, analog to get_dig_params and get_hit_params.

It also fixes a minor mistake in the function comments. add_wear claims to support only a range of [0,65535] but this is false, it also supports 65536 (which leads to insta-break). I checked this.

Context

The common (and naive) way that mods usually implement "tool break after n usesis by adding wear withtool:add_wear(some_fixed_value)in whichsome_fixed_valueis chosen in a way that the tool breaks after exactlyntimes. This works for small numbers ofn(<273) but asnincreases you might actually not be able to hitn` exactly due to rounding. As an extreme example, with this method you can't have a tool with exactly 50000 uses, but must decide 32768 or 65536 uses (adding 2 or 1 wear at every use, respectively).
That's where the helper function comes into play.

This PR builds on the work done in #11110 and is basically an extension of the logic used there for mods. It uses calculateResultWear for the calcuation. Read this PR for more context.

Note the actual math is NOT altered by this PR in any way. It basically just exposes the "tool uses before it breaks" calculation the engine already uses to Lua.

To do

This PR is ready for review.

How to test

• Activate luacmd
• Give yourself any tool with 0 wear and wield it
• /lua n=60000; p=0; x=me:get_wielded_item(); for i=1,65536 do x:add_wear_by_uses(n); p=p+1; if x:get_count()==0 then break end end print(p); me:set_wielded_item(x)
• This is a loop that calls add_wear_by_uses(n) n times, so the tool must break after exactly n uses. At the end, it prints out how many iterations this look actually had
• Since n is 60000 in this case, it should print out 60000
• Replace the value of n with different values, including 0 (=infinite uses), 65535 or 65536
• The other function can be tested in a similar fashion
• Also try manually calling these functions without a loop to see how the wear bar reacts

[ghost]

This would be cool.

[ghost]

Tested with all integers between [0 .. 65537]

• 0 and 65537 never broke
• All other values broke in the expected number of uses

At a glance, behavior seems correct. Will test more and finish review tomorrow.

[ghost]

Looked over the code, also did some further manual testing mixing uses values and behavior seemed sensible. Looks good to me.

[sfan5]

just as information: I don't think it's necessary to put detailed documentation here, btw

[sfan5]

If you have time it'd also be nice to see unittests in devtest for this API function.

[Wuzzy2]

I fixed the broken bullet points and I renamed the arg.

[sfan5]

Looks good.