[Proposal]: Simple lambda parameters with modifiers (VS 18.0, .NET 10)

# Simple lambda parameters with modifiers

* Specification: https://github.com/dotnet/csharplang/blob/main/proposals/csharp-14.0/simple-lambda-parameters-with-modifiers.md
* Discussion: [Link to the discussion topic for this feature.](https://github.com/dotnet/csharplang/discussions/8636)

## Summary
[summary]: #summary

Allow lambda parameters to be declared with modifiers without requiring their type names. For example, `(ref entry) => ...` rather than `(ref FileSystemEntry entry) => ...`.

## Design meetings

* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-02-21.md#declaration-of-refout-parameters-in-lambdas-without-typename
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-10-16.md#simple-lambda-parameters
* https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-12-09.md#simple-lambda-parameters
* https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-01-15.md#simple-lambda-parameters