Use public direct links for object for S3 and Azure

[shcheklein]

Followup #755

Less critical of implementation since it affects only public, no credentials buckets and Studio teams. It works already for Google Storage since @dreadatour fixed it a while ago.

Public S3 and Azure client.url() code. Similar to GS that already has a check for anon in it - we need to generate and return direct URL to the cloud storage.

Make sure along the way:

• Endpoint URLs are supported, especially for AWS
• On the Studio side pass ms header to signed URL to get a public URL that actually works (see some SO discussions)
• add tests

[dreadatour]

Quick note: I have checked AWS S3 and it returns public URL out of the box if no credentials found:

In [1]: from datachain.catalog import get_catalog

In [2]: catalog = get_catalog()

In [3]: catalog.signed_url('s3://fast-ai-nlp', 'ag_news_csv.tgz')
Out[3]: 'https://fast-ai-nlp.s3.amazonaws.com/ag_news_csv.tgz'

This URL is actually works: https://fast-ai-nlp.s3.amazonaws.com/ag_news_csv.tgz

We still need to check all possible options for S3 and Azure.

[shcheklein]

Thing to check for S3 if it works for versioned files (when you pass version_id)