Improve SyntaxRewriter performance for operator folding

Running operator folding on MovieSwiftUI takes as long as parsing. That really shouldn’t be the case. Running with Instruments shows that we spend the majority of time in memory-related operations.

The first steps to take would be:
- Add an `arena` parameter to all the syntax node initializers
- Add an `arena` parameter to `SyntaxRewriter`
- Construct all nodes in `SyntaxRewriter` and operator folding in that arena
- Investigate where else `SyntaxRewriter` is causing memory allocations and try to eliminate them

Attached is a WIP diff where I started to eliminate some of the memory allocations by `SyntaxRewriter` but I stopped once I realized that we’d need to modify the initializers of all syntax nodes.

[reduce-arena-memory-allocations.txt](https://github.com/apple/swift-syntax/files/12297749/reduce-arena-memory-allocations.txt)