Improve add syntax for lists by saving the last used index

[Shroobz]

Problem

Adding to lists has been slow due to an O(N) lookup happening every single time a value is added. This means adding N values to a list separately is O(N²), while adding them all at the same time is O(N). This problem is also described in #891

Solution

I (somewhat) solved this problem in 2 ways:
1: Replaced repeated TreeMap.containsKey() calls with HashSet.contains() calls
2: Saving the last used index during an add operation. If another operation is done that could cause a gap in the list, the saved index is reset. This means the O(N) lookup will only happen once a gap can occur or when the server restarts.

Testing Completed

quickTest was completed succesfully. I tested if gaps in lists would get filled and the performance of the code in #891 (the performance is now pretty much the same for setting and adding, adding might even be faster (though I doubt it))

Supporting Information

---

Completes:: #891
Related: #891
AI assistance: none

p.s. I think some sort of auto formatter ran and removed a double tab around line 242

[Efnilite]

some benchmarks may be nice to show the actual improvement (and whether there is one)

[Shroobz]

some benchmarks may be nice to show the actual improvement (and whether there is one)

I have no idea how I forgot those, here:

Before	After

function test_blockloop_add(radius: integer, location: location):
  delete {blocks::*}
  set {_time} to now
  loop blocks in radius {_radius} around {_location}:
    add loop-block to {blocks::*}
  
  broadcast "It took %difference between now and {_time}% to loop blocks in a radius of %{_radius}% and add them to a list using add syntax."
  broadcast "%size of {blocks::*}% values were set"

function test_blockloop_set(radius: integer, location: location):
  delete {blocks::*}
  set {_time} to now
  set {_i} to 0
  loop blocks in radius {_radius} around {_location}:
    set {blocks::%{_i}%} to loop-block
    add 1 to {_i}
  broadcast "It took %difference between now and {_time}% to loop blocks in a radius of %{_radius}% and add them to a list using set syntax."
  broadcast "%{_i}% values were set"

[Shroobz]

I forgot to rename the usages of lastUsedIndex, 1 sec

[Efnilite]

some benchmarks may be nice to show the actual improvement (and whether there is one)

I have no idea how I forgot those, here:
Before After

😝

[UnderscoreTud]

This is a duplicate of #8519

[Shroobz]

This is a duplicate of #8519

no idea how I didn't see that, sorry

[UnderscoreTud]

It's okay, we still appreciate your contribution! It's partly my fault for not referencing the issue you referenced (I didn't know it existed :p). Don't let this push you away from contributing in the future!