Change: start moving groups section out of manage_sql.c

[mattmundell]

What

Move a few functions from the groups section in manage_sql.c to dedicated groups files.

Why

To reduce the size of manage_sql.c and to better organise the GMP resources.

References

Similar to #2523 for assets.

Testing

I ran GET_GROUPS with the PR and with main, and compared the output:

o m m '<get_groups/>' > /tmp/g-pr
o m m '<get_groups trash="1"/>' > /tmp/g-pr-tr
o m m '<get_groups/>' > /tmp/g-main
o m m '<get_groups trash="1"/>' > /tmp/g-main-tr
diff /tmp/g-main /tmp/g-pr
diff /tmp/g-main-tr /tmp/g-pr-tr