Cleanup Monorail components in histograms.xml files

Leaving tools/metrics/histograms/metadata/apps/histograms.xml out for now because I can't find/access the corresponding Buganizer component. Will create a separate CL for that file.

Adding a DIR_METADATA file for bookmarks/histograms.xml because most of the histograms in the file are associated with component UI>Browser>Bookmarks.

Some histograms have their <component> tags removed because the same component is already associated with the histogram through OWNERS or directory level DIR_METADATA.

Change-Id: Ib564407253dbd7fa6fc3b47e5dd64f210615e81f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5473443


Commit-Queue: Ariel Zhang <arielzhang@google.com>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Luc Nguyen <lucnguyen@google.com>
Cr-Commit-Position: refs/heads/main@{#1291987}