[buganizer] Migrate DIR_METADATA for net/ and sql/

Migrate all metadata files for net/ and sql/ and mixins
used by metadata files under net/ and sql/.

Verify components with http://b/components/{id} or at
go/chrome-on-buganizer-prod-components.

Bug: chromium:1518875
Change-Id: I2d081a94bb40e0f1e8638582976787a4ae5fa000
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5203309
Reviewed-by: Chris Fredrickson <cfredric@chromium.org>
Reviewed-by: Adam Langley <agl@chromium.org>
Commit-Queue: Jeff Yoon <jeffyoon@google.com>
Reviewed-by: Ayu Ishii <ayui@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1248393}