Change: move first few role functions to dedicated files

[mattmundell]

What

Move first few functions out of the Roles section of manage_sql.c.

Why

Reduces the size of manage_sql.c to make it easier to work with. Also for better organization of the resources.

References

Similar to #2694 for Groups.

Testing

I ran gvmd --get-roles. Looked OK.

I also ran GET_GROUPS, comparing the output to main:

# on main
o m m '<get_roles/>' > /tmp/r-main
o m m '<get_roles trash="1"/>' > /tmp/r-main-trash
# with pr
o m m '<get_roles/>' > /tmp/r-pr
o m m '<get_roles trash="1"/>' > /tmp/r-pr-trash
diff /tmp/r-main /tmp/r-pr
diff /tmp