Align CSLA 11 release notes with the v10.x format

[rockfordlhotka]

Closes #4937

Restructures releasenotes.md on main so the CSLA 11 notes follow the same format as the CSLA 10 notes on v10.x:

• Intro: says 11.0.0 includes everything in 10.2.0, and the compare link now starts at the new v10.2.0 tag instead of v10.1.0. The separate "Change List" section is folded into it, as in the 10.1.0 and 10.2.0 notes.
• Highlights: a "Platform Updates" block for .NET 11 support and dropping .NET 8 and 9 (Add support for .NET 11 #4699, Remove support for .NET 8 #4348, Remove support for .NET 9 #4581, Target .NET 10 and 11; remove .NET 8 and 9 #4922), including the new net11.0 MAUI targets.
• Changes: a "Build and Release" category with Set main version to 11.0.0-alpha.1 #4917.
• Breaking Changes: adds that on .NET 11, Android apps using Csla.Maui need API level 24 (from Target .NET 10 and 11; remove .NET 8 and 9 #4922).

Supported Platforms and Contributors are unchanged. Only #4922 and #4918 are on main and not on v10.x, and both are by @rockfordlhotka.

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