feat: move NpmPackageId from deno_npm

[dsherret]

Going to move this down here even though I liked it in deno_npm because I need this for deno_lockfile, but deno_npm depends on deno_lockfile. I could create deno_npm_types, but that seems like an unnecessary maintenance burden.

https://github.com/denoland/deno_npm/blob/f409ede427a6f38a35204cbedfa928487d0c835b/src/lib.rs#L29-L32

[dsherret]

I just realized this is not necessary. That said, I want to integrate some of these changes back into deno_npm so I'll leave this as draft until that's done.