[Proposal]: extension methods, properties and operators (VS 18.0, .NET 10)

# Extensions

* Specifications:
https://github.com/dotnet/csharplang/blob/main/proposals/csharp-14.0/extensions.md
https://github.com/dotnet/csharplang/blob/main/proposals/csharp-14.0/extension-operators.md
* Working group folder: https://github.com/dotnet/csharplang/tree/main/meetings/working-groups/extensions
* Discussion: https://github.com/dotnet/csharplang/discussions/8696

## Summary

We add the ability to declare extensions for any type of member, including static methods, constructor, properties, operators, and more.

## LDM Meetings

* https://github.com/dotnet/csharplang/blob/main/meetings/2021/LDM-2021-12-01.md#roles-and-extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-08-31.md#roles
* https://github.com/dotnet/csharplang/blob/main/meetings/2022/LDM-2022-09-26.md#roles--extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-02-22.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-12-11.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-02-28.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-06-12.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-06-26.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-07-22.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-09-18.md#extensions-naming
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-09-30.md
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-02.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-07.md
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-09.md
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-14.md
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-30.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-11-13.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-11-20.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-01-06.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-01-22.md#extensions-disambiguation-syntax
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-02-19.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-02-24.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-02-26.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-03-17.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-03-24.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-04-16.md
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-04-23.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-05-05.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-04.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-09.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-11.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-18.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-23.md#extensions
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-08-18.md#extensions