[turbopack] Simplify `Request::parse(Pattern)` the recursive portion doesn't need to be async (#80510)
## Optimize Request parsing in Turbopack core resolver
### What?
Refactored the `Request::parse_ref` method and related functions to improve performance by:
- Converting async functions to synchronous where possible
- Normalizing patterns before parsing to improve cache hits
- Handling alternatives pattern separately in the async `parse_inner` function
- Adopt `rcstr!` in a few places
### Why?
This should be a small perf enhancement, basically just noticed the `Box::pin` calls and decided to track down what was fundamentally async.