Support for concurrent package registry requests when using `--enrich`

What would you like to be added:

Support for making package registry requests concurrently when using --enrich.

At the moment, enrichment requests appear to be made synchronously/sequentially. I verified this by running Syft with verbose logging:

SYFT_CACHE_DIR=/tmp/syft-cache syft file:pnpm-lock.yaml \
  --select-catalogers npm \
  --enrich javascript \
  -o spdx-json=pnpm.sbom.json \
  -vvvv

It would be useful if Syft could perform registry lookups in parallel, ideally with a configurable concurrency limit to avoid overwhelming package registries or hitting rate limits.

Why is this needed:

For large lockfiles, synchronous enrichment makes SBOM generation very slow.

In my case, pnpm-lock.yaml contained more than 1,500 packages, and the command above took approximately 10 minutes to complete.

Most of the elapsed time appears to be spent waiting for package registry responses. Since these lookups are largely independent of one another, running a bounded number of requests concurrently could significantly reduce overall SBOM generation time.

Additional Context:

Syft version: 1.51.0