Refactor: libcrmcommon: Move some XML constants to better location

Three XML element constants that follow the current naming convention
were in the "Older constants that don't follow current naming" section
of msg_xml.h, next to their logical families. This commit moves them to
the top, under "XML elements".

Also use spaces instead of tabs in these top sections, as well as
alphabetical order.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>