enrich version --long's output with build deps

[alessio]

The output of the version --long command now shows
the list of build dependencies.

From: #7848
Closes: #7835

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #7864 (33e0a0d) into launchpad/backports (c4f4d03) will not change coverage.
The diff coverage is n/a.

@@                 Coverage Diff                  @@
##           launchpad/backports    #7864   +/-   ##
====================================================
  Coverage                50.26%   50.26%           
====================================================
  Files                      338      338           
  Lines                    17560    17560           
====================================================
  Hits                      8827     8827           
  Misses                    7940     7940           
  Partials                   793      793           

[ethanfrey]

Ack

[clevinson]

ACK