feat: requestList accepts proxyConfiguration for requestsFromUrls

[barjin]

closes #1073

Intended use:

const proxyConfiguration = await Apify.createProxyConfiguration({ 
    // the proxy is to be specified here 
});

 const requestList = await Apify.openRequestList('test',[
        { requestsFromUrl:'http://sitemap.txt/sitemap.txt' }
    ], { proxyConfiguration }
 );

[B4nan]

looking good, please add at least one test that verifies the proxy is being actually used (can be just a unit test)

[B4nan]

lets see how this will work with the old docs (it should work fine with the sdk 3 ts api docs, but here - god knows)

[pocesar]

LGTM, thanks @barjin !

[B4nan]

dont forget to migrate this to jest when backporting (no need to do it now, we can backport larger chunk later)