[WIP] PR: Add remote-files capability to remote-client plugin

[hlouzada]

Description of Changes

• Wrote at least one-line docstrings (for any new functions)
• Added unit test(s) covering the changes (if testable)

Add remote files system API using fsspec for the remote-client plugin.

Use a mixture of rest/websocket to comunicate with spyder-remote-services and
provide a filesystem-like API to control remote file system.

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: @hlouzada

[pep8speaks]

Hello @hlouzada! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file spyder/plugins/remoteclient/api/jupyterhub/files.py:

Line 34:80: E501 line too long (82 > 79 characters)
Line 78:80: E501 line too long (80 > 79 characters)
Line 79:80: E501 line too long (80 > 79 characters)
Line 101:13: E722 do not use bare 'except'
Line 116:80: E501 line too long (83 > 79 characters)
Line 124:1: W293 blank line contains whitespace
Line 131:1: E302 expected 2 blank lines, found 1