Add metatable to correctly handle FSO objects

[BMagnu]

Consider the following script:

table = {mn.Teams["Friendly"] = 0}
print(table[mn.Teams["Friendly"]]) -- will print nil

This rather unintuitive behaviour is because lua table lookups are by rawequal. As teams, and basically all FSO objects, are userdata, their rawequal check does not call metamethods, and thus does not respect the built-in equality operators for FSO userdata. Instead, userdata is just checked against same instance, which is not the case for the example script.
This PR adds a metatable which changes this by explicitly calling == instead, overwriting or querying entries that are semantically equal but not rawequal.
When using FSO-userdata as table keys, this is almost always the intended behaviour (though with correct design in some circumstances rawequal can suffice as well, but semantically equal would work just as well).

So with this PR, the upper example could be made to work as follows:

table = {mn.Teams["Friendly"] = 0}
setmetatable(table, Globals.FSOObjectsTableMetatable)
print(table[mn.Teams["Friendly"]]) -- will print 0

Of course, a user could write / paste the entire metatable and not need this PR, but its such a common usecase and footgun that I'd like to include it in our globals.

[Goober5000]

This will be very useful 👍

[BMagnu]

Found a possible bug

[BMagnu]

Fixed, dunno how this didn't came up in the initial tests