Update to latest Ultralight

[SupinePandora43]

• [x] ULString marshalling
• [x] Use nint/nuint for ssize_t/size_t
• [x] Re-enable net45,net451,nestandard2,netstandard2.1
• • [x] Port generated output to older TFs
• • • [x] Remove TF-dependent api use from generated files
• [ ] Test everything
• [ ] Benchmark
• • [x] Opaque ULString
• • • [x] Managed UTF8 conversion vs tmp ULString
• • [x] Marshal.GetDelegateForFunctionPointer vs () => functionPointer() (marshal is slower almost 6 times in allocation and 1.44 in calling)
• [x] Unsafe.SkipInit in structs (config/viewconfig)

[codecov-commenter]

Codecov Report

Merging #45 (419f0f7) into master (dcf8a5a) will increase coverage by 9.23%. The diff coverage is n/a.

:exclamation: Current head 419f0f7 differs from pull request most recent head 5eb3a2d. Consider uploading reports for the commit 5eb3a2d to get more accurate results

@@            Coverage Diff             @@
##           master      #45      +/-   ##
==========================================
+ Coverage   25.32%   34.55%   +9.23%     
==========================================
  Files          31       57      +26     
  Lines        1619     2839    +1220     
  Branches      119      353     +234     
==========================================
+ Hits          410      981     +571     
- Misses       1209     1858     +649     

Impacted Files	Coverage Δ
src/UltralightNet/Structs/ULCommand.cs	50.00% <0.00%> (ø)
src/UltralightNet/ULViewConfig.cs	64.06% <0.00%> (ø)
src/UltralightNet/Structs/ULIntRect.cs	85.71% <0.00%> (ø)
src/UltralightNet.Test/RendererFixture.cs	100.00% <0.00%> (ø)
.../UltralightNet/JavaScript/Structs/JSStaticValue.cs	0.00% <0.00%> (ø)
src/UltralightNet/ULConfig.cs	88.88% <0.00%> (ø)
src/UltralightNet.AppCore/ULMonitor.cs	0.00% <0.00%> (ø)
src/UltralightNet.Test/ULRects.Test.cs	0.00% <0.00%> (ø)
src/UltralightNet/Structs/ULLogger.cs	30.00% <0.00%> (ø)
src/UltralightNet/Structs/ULFontLoader.cs	25.00% <0.00%> (ø)
... and 47 more

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[SupinePandora43]

Gonna do a giant cleanup rn

[SupinePandora43]

Only GitHub CQ CI is broken - i will remove it, because it's practically useless.

• [x] Gonna merge, when new Ultralight bins with fixed c api comes out.

.NET7 and proper [LibraryImport] generator work will begin in November, after .NET7 release - no perf-critical changes should be expected.

[SupinePandora43]

i don't trust CI because my local managed filesystem tests fail, but i will merge it just to update nuget.