Use the `instance()` method for all `NativeConverter` implementations

[ExE-Boss]

This makes it so that when I make a change to a NativeConverter implementation, I don’t forget to update any usage of said NativeConverter implementation and get a nova.core.nativewrapper.NativeManager.NativeException: Cannot find native converter for: <class> or a ClassCastException.

[codecov-io]

Codecov Report

Merging #309 into master will increase coverage by 0.17%. The diff coverage is 2.72%.

@@             Coverage Diff              @@
##             master     #309      +/-   ##
============================================
+ Coverage     16.37%   16.54%   +0.17%     
- Complexity      931      960      +29     
============================================
  Files           416      416              
  Lines         13170    13147      -23     
  Branches       1381     1383       +2     
============================================
+ Hits           2156     2175      +19     
+ Misses        10870    10827      -43     
- Partials        144      145       +1

Impacted Files	Coverage Δ	Complexity Δ
...in/java/nova/core/nativewrapper/NativeManager.java	51.06% <ø> (-1.02%)	6 <0> (ø)
...r/mc/forge/v17/wrapper/entity/EntityConverter.java	0% <ø> (ø)	0 <0> (ø)	:arrow_down:
...apper/mc/forge/v18/wrapper/item/BWItemFactory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...wrapper/mc/forge/v17/launcher/FMLEventHandler.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
.../mc/forge/v17/wrapper/entity/forward/FWEntity.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...wrapper/mc/forge/v18/launcher/FMLEventHandler.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
.../mc/forge/v17/wrapper/item/ItemWrapperMethods.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...mc/forge/v17/network/discriminator/NovaPacket.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...er/mc/forge/v18/wrapper/inventory/BWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...apper/mc/forge/v17/manager/MCRetentionManager.java	4.25% <0%> (ø)	1 <0> (ø)	:arrow_down:
... and 50 more

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