Porting new docs for the System namespace

[tannergooding]

This handles most of dotnet/runtime#88563. There are some APIs that are missing xml docs entirely that still need to be handled.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[gewarren]

I haven't finished, but wanted to send these through meanwhile.

[gewarren]

Finished with my review now.

[learn-build-service-prod]

Learn Build status updates of commit cea4f6b:

❌ Validation status: errors

Please follow instructions here which may help to resolve issue.

File	Status	Preview URL	Details
	❌Error		Details
xml/System/GC.xml	❌Error		Details

• Line 0, Column 0: [Error: ECMA2Yaml_File_LoadFailed] Failed to load 1 files, aborting...

xml/System/GC.xml

• Line 0, Column 0: [Error: ECMA2Yaml_InternalError]

Intenal Several Error: System.ArgumentException: An item with the same key has already been added. Key: totalSize
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at ECMA2Yaml.ECMALoader.LoadDocs(XElement dElement, String filePath)
   at ECMA2Yaml.ECMALoader.LoadMember(Type t, XElement mElement)
   at System.Linq.Enumerable.SelectEnumerableIterator`2.ToList()
   at ECMA2Yaml.ECMALoader.LoadType(FileItem typeFile)
   at ECMA2Yaml.ECMALoader.LoadTypes(String basePath, Namespace ns)

For more details, please refer to the build report.

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[learn-build-service-prod]

Learn Build status updates of commit 989a50e:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System/ArgumentException.xml	✅Succeeded	View
xml/System/ArgumentOutOfRangeException.xml	✅Succeeded	View
xml/System/Byte.xml	✅Succeeded	View
xml/System/Char.xml	✅Succeeded	View
xml/System/DateOnly.xml	✅Succeeded	View
xml/System/DateTime.xml	✅Succeeded	View
xml/System/DateTimeOffset.xml	✅Succeeded	View
xml/System/Decimal.xml	✅Succeeded	View
xml/System/Delegate.xml	✅Succeeded	View
xml/System/Double.xml	✅Succeeded	View
xml/System/Enum.xml	✅Succeeded	View
xml/System/Environment.xml	✅Succeeded	View
xml/System/GC.xml	✅Succeeded	View
xml/System/Half.xml	✅Succeeded	View
xml/System/Int128.xml	✅Succeeded	View
xml/System/Int16.xml	✅Succeeded	View
xml/System/Int32.xml	✅Succeeded	View
xml/System/Int64.xml	✅Succeeded	View
xml/System/IntPtr.xml	✅Succeeded	View
xml/System/IUtf8SpanFormattable.xml	✅Succeeded	View
xml/System/MemoryExtensions.xml	✅Succeeded	View
xml/System/MulticastDelegate.xml	✅Succeeded	View
xml/System/OperatingSystem.xml	✅Succeeded	View
xml/System/Random.xml	✅Succeeded	View
xml/System/SByte.xml	✅Succeeded	View

This comment lists only the first 25 files in the pull request.
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[tannergooding]

@gewarren, I believe all the feedback (thanks for being so thorough!) has been accounted for and a new description for the TimeProvider case has been provided.

Please let me know if any other changes are needed.