[WIP] pinning remediation advice for Python

[kyegupov]

• Ready for review
• Follows CONTRIBUTING rules
• Reviewed by Snyk internal team

What does this PR do?

Experimental implementation of pinning for the Python ecosystem.

[snyksec]

	Fails
🚫	Commit "Added output test for non-actionable-remediation mode" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "complete test for the output" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "remove test only" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "Show paths information" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "Show upgrades before paths" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "offer upgrades as alternative to pins" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "Added tests" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "spike: pinned are not unresolved" is not a valid commitizen message. See Contributing page with required commit message format.
🚫	Commit "spike: pinning remediation advice for Python" is not a valid commitizen message. See Contributing page with required commit message format.

	Messages
📖	This PR will not trigger a new version. It doesn't include any commit message with feat or fix.

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