bundle-uri client: add boolean transfer.bundleURI setting

bundle-uri client: add boolean transfer.bundleURI setting

The yet-to-be introduced client support for bundle-uri will always
fall back on a full clone, but we'd still like to be able to ignore a
server's bundle-uri advertisement entirely.

The new transfer.bundleURI config option defaults to 'false', but a user
can set it to 'true' to enable checking for bundle URIs from the origin
Git server using protocol v2.

Co-authored-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>