Change: move first functions to dedicated user files

[mattmundell]

What

Move first functions out of the Users section of manage_sql.c.

Why

Reducing the size of manage_sql.c. Making locations of per-resource code consistent.

References

Similar to /pull/2705 for roles.

Testing

I ran GET_USERS, comparing output with main.

# on main
o m m '<get_users/>' > /tmp/u-main
# with pr
o m m '<get_users/>' > /tmp/u-pr
diff /tmp/u-main /tmp/u-pr

I also created and cloned users in GSA.