repo: add the field layout.bare

repo: add the field layout.bare

This commit is part of the series that introduces the new subcommand
git-repo-info.

The flag --is-bare-repository from git-rev-parse is used for retrieving
whether the current repository is bare. This way, it is used for
querying repository metadata, fitting in the purpose of git-repo-info.

Then, add a new field layout.bare to the git-repo-info subcommand
containing that information.

Helped-by: Phillip Wood <redacted>
Helped-by: Junio C Hamano <redacted>
Helped-by: Justin Tobler <redacted>
Helped-by: Eric Sunshine <redacted>
Mentored-by: Karthik Nayak <redacted>
Mentored-by: Patrick Steinhardt <redacted>
Signed-off-by: Lucas Seiki Oshiro <redacted>
Signed-off-by: Junio C Hamano <redacted>