submodule-config: "goto" removal in parse_config()

submodule-config: "goto" removal in parse_config()

Many components in if/else if/... cascade jumped to a shared
clean-up with "goto release_return", but we can restructure the
function a bit and make them disappear, which reduces the line count
as well.  Also reformat overlong lines and poorly indented ones
while at it.

The order of rules to verify the value for "ignore" used to be to
complain on multiple values first and then complain to boolean, but
swap the order to match how the values for "path" and "url" are
verified.

CC: Eric Sunshine <sunshine@sunshineco.com>
CC: Heiko Voigt <hvoigt@hvoigt.net>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>