sysutils/tracker3: add SOUP2 and SOUP3 multi options
Because Tracker can support libsoup2 and libsoup3 backend, and also at
the same time, it makes sense to add a multi option to give the user the
possibility of selecting them.
The default is still libsoup2, so the default dependencies of this port
will not change at this time.
PR: 272017
MFH: 2023Q2