Fix CharSegment Equals

[CharSegment](https://github.com/linksplatform/Collections/blob/3643cf14cbf82df06b22df1ec7f9dd0bc5c68f8d/csharp/Platform.Collections/Segments/CharSegment.cs) has bug in [Equals](https://github.com/linksplatform/Collections/blob/3643cf14cbf82df06b22df1ec7f9dd0bc5c68f8d/csharp/Platform.Collections/Segments/CharSegment.cs#L31-L46) method
https://github.com/linksplatform/Collections/blob/3643cf14cbf82df06b22df1ec7f9dd0bc5c68f8d/csharp/Platform.Collections/Segments/CharSegment.cs#L31-L46

Fix it
Small example [use this [sandbox](https://github.com/Konard/LinksPlatform/blob/master/Platform/Platform.Sandbox/AllRepeatingSubstringsInString.cs) and add property `PublicDictionary` to `Walker4`]:
```csharp
/*
public IDictionary PublicDictionary
{
get => Dictionary;
}
*/

var text = "aaaaaaaaaa";
var walker = new Walker4();
walker.WalkAll(text);
foreach (var l in walker.PublicDictionary)
{
foreach (var r in walker.PublicDictionary)
{
Console.WriteLine($"{l} == {r} ==> {l.Key.Equals(r.Key)}");
}
}

```

Start with csharp/Platform.Collections/Segments/CharSegment.cs and inspect the Equals method at the linked lines. Use the linked AllRepeatingSubstringsInString.cs sandbox and the proposed Walker4 PublicDictionary example to reproduce the incorrect comparisons. Done means equivalent CharSegment instances compare correctly in that example.

Written by the indexing model from the issue text.