accept stage paths starting with / for GET

[sfc-gh-tvanderkooy]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-1793953 (SNOW-1889627: SNOW-1793953: Allow relative path starting with / for GET #2888)

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines

3. Please describe how your code solves the related issue.

   This builds on the changes from Add support for snow:// stage paths #1346 to allow / as a remote path prefix so file.get('/some/path')will not try to prepend @ to the path. This form of relative path is valid in some native application uses cases.

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[sfc-gh-tvanderkooy]

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[sfc-gh-aalam]

@sfc-gh-tvanderkooy can you fix the failing tests please. change looks good

[sfc-gh-tvanderkooy]

Turns out the test failures were because my change breaks #2470, which adds an explicit error for using a non-stage path with session.read.<file_format>(<path). These functions reads files from a stage that are some table format (avro, csv, etc.) into a data frame, and the error is to help users that are trying to use these functions with local files (which doesn't work).

I think it's unlikely for native app providers to want to use this in their app -- any file that is valid for these functions they could simply share as a table instead of putting as a file in the version stage -- so I opted to NOT support the relative stage path syntax for this case and preserve the existing error message.

cc @sfc-gh-jrose @sfc-gh-aalam

[sfc-gh-aalam]

this change adds support when run inside a native apps environment. How does it affect when run outside NA? If it is not supported, then we should only allow the new prefix in NA env.

[sfc-gh-tvanderkooy]

Outside native apps this will be a SQL error. SQL compilation error: invalid URL prefix found in: '/some/path'

But that's the current behaviour too (for GET) - today if you do session.file.get('/some/path'), snowpark will prepend @ and run the GET, and then throw SQL compilation error: missing stage name in URL: @/some/path

Unfortunately I'm not aware of a good way to check if this is NA env, it might be difficult to check that here.