JSEP: Use global-agent in scripts to enable using network proxy (#22537)
This PR add dependency to the global-agent package, and use it in JSEP
scripts that download files from network (i.e. `js/scripts/utils.ts` and
`js/web/script/pull-prebuilt-wasm-artifacts.ts`), so that user can make
these script use network proxy by setting environment variable
GLOBAL_AGENT_HTTPS_PROXY.