feat: Refactor inventory

[ExE-Boss]

List of changes:

• Completed InventoryIterator to match the spec
• Improved the Inventory interface
  • Completed JavaDoc
  • Now uses java.util.Optional instead of null
  • Methods now throw java.lang.IndexOutOfBoundsException if the requested slot is out of bounds (fixes #188)

[codecov[bot]]

Codecov Report

Merging #324 into master will decrease coverage by 0.02%. The diff coverage is 1%.

@@             Coverage Diff              @@
##             master     #324      +/-   ##
============================================
- Coverage     13.24%   13.21%   -0.03%     
- Complexity     1005     1006       +1     
============================================
  Files           532      532              
  Lines         17368    17429      +61     
  Branches       1803     1818      +15     
============================================
+ Hits           2301     2304       +3     
- Misses        14920    14978      +58     
  Partials        147      147

Impacted Files	Coverage Δ	Complexity Δ
.../java/nova/core/component/inventory/Inventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...c/forge/v1_11_2/wrapper/inventory/FWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...r/mc/forge/v1_8/wrapper/inventory/BWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...c/forge/v1_7_10/wrapper/inventory/BWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...r/mc/forge/v1_8/wrapper/inventory/FWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
src/main/java/nova/core/item/Item.java	30.95% <0%> (ø)	9 <0> (ø)	:arrow_down:
...a/nova/core/component/inventory/InventoryView.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...c/forge/v1_11_2/wrapper/inventory/BWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...c/forge/v1_7_10/wrapper/inventory/FWInventory.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
...nova/core/component/inventory/InventorySimple.java	0% <0%> (ø)	0 <0> (ø)	:arrow_down:
... and 1 more

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[RX14]

The original rule of thumb was that we accept nulls into arguments and return optionals.