[parsing] Deprecate PopulateUpstreamToDrake

[jwnimmer-tri]

Part of #10531.

This should have been concomitant with #15947, but we overlooked it. Since we don't have any more non-root manifests (outside of unit tests), we don't need any function or automation to find them.

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This change is 

[jwnimmer-tri]

\CC @EricCousineau-TRI @cottsay FYI

+@sammy-tri for feature review, please?
+@rpoyner-tri for platform review per schedule, please.

[sammy-tri]

Reviewed 12 of 12 files at r1, all commit messages.
Reviewable status: 1 unresolved discussion, LGTM missing from assignees rpoyner-tri(platform),sammy-tri(platform) (waiting on @jwnimmer-tri and @rpoyner-tri)

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multibody/parsing/parser.cc, line 47 at r1 (raw file):

  // Always search for a package.xml file, starting the crawl upward from
  // the file's path.
  package_map_.PopulateUpstreamToDrake(file_name);

If this function is a no-op now, why not delete the call instead of ignoring the deprecation? (and if it's still doing something, that should probably be explained somewhere)

[jwnimmer-tri]

Reviewable status: 1 unresolved discussion, LGTM missing from assignees rpoyner-tri(platform),sammy-tri(platform) (waiting on @rpoyner-tri and @sammy-tri)

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multibody/parsing/parser.cc, line 47 at r1 (raw file):

Previously, sammy-tri (Sam Creasey) wrote…

If this function is a no-op now, why not delete the call instead of ignoring the deprecation? (and if it's still doing something, that should probably be explained somewhere)

Done.

The deprecation comment was somewhat imprecise; I've amended it.

In cases where the user is relying on a deprecated package.xml file that lives within Drake directly (e.g., [1]), it is not a no-op. In any other case, it is a no-op. For now, the parser needs to backfill this search path, but once those files are removed, we can remove this line (even while leaving the deprecated function intact until 05-01).

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[1] For example:

drake/manipulation/models/franka_description/package.xml

Lines 15 to 19 in a064a74

	<deprecated>
	The 'package://franka_description' URI spelling is deprecated, and will be
	removed from Drake on or around 2022-03-01. Please spell the URI as
	'package://drake/manipulation/models/franka_description' instead.
	</deprecated>

[jwnimmer-tri]

+@rpoyner-tri for platform review per schedule, please.

[sammy-tri]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: LGTM missing from assignee rpoyner-tri(platform) (waiting on @rpoyner-tri)

[rpoyner-tri]

Reviewed 10 of 12 files at r1, 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all discussions resolved, LGTM from assignees rpoyner-tri(platform),sammy-tri(platform) (waiting on @jwnimmer-tri)