add warning-risk for deprecated packages

[memsharded]

Changelog: Fix: Add warning for deprecated attribute in recipes.
Docs: conan-io/docs#4041

Close #17952

[uilianries]

I would include the case deprecated = "foobar", where the warning message suggests to use foobar as replacement for the deprecated reference.

[memsharded]

I would include the case deprecated = "foobar", where the warning message suggests to use foobar as replacement for the deprecated reference.

@uilianries The deprecation is already showing the reason:

    if deprecated:
        output.info("Deprecated", Color.BRIGHT_YELLOW)
        for d, reason in deprecated.items():
            reason = f": {reason}" if reason else ""
            output.info("    {}{}".format(d, reason), Color.BRIGHT_CYAN)

[uilianries]

LGTM. Thank you for backporting it!