Python: avoid selecting getLocation()

[nickrolfe]

For Python this doesn't seem to be as disastrous as for C# and Java: the evaluator logs suggest Location::toString() was getting magicked in UnnecessaryDelete.ql, so it wasn't causing any performance issues, but I've fixed it anyway.

For TruncatedDivision.ql, meanwhile, this change means we avoid generating these predicates:

[2023-06-05 10:48:09] Evaluated non-recursive predicate Files#a547fcb4::Location::toString#0#dispred#ff@cb160078 in 2432ms (size: 2278502).
Evaluated relational algebra for predicate Files#a547fcb4::Location::toString#0#dispred#ff@cb160078 with tuple counts:
              0   ~0%    {2} r1 = SCAN Files#a547fcb4::EncodingError#f OUTPUT In.0, "Encoding Error"
                     
              0   ~0%    {2} r2 = SCAN Files#a547fcb4::SyntaxError#f OUTPUT In.0, "Syntax Error"
              0   ~0%    {2} r3 = r2 AND NOT Files#a547fcb4::EncodingError#f(Lhs.0)
                     
        2278502   ~3%    {2} r4 = SCAN Files#a547fcb4::Location::getPath#0#dispred#ff OUTPUT In.1, In.0
        2278502   ~2%    {2} r5 = JOIN r4 WITH Files#a547fcb4::Container::getAbsolutePath#0#dispred#ff ON FIRST 1 OUTPUT Lhs.1, Rhs.1
        2278502   ~2%    {2} r6 = r5 AND NOT Files#a547fcb4::SyntaxError#f(Lhs.0)
        2278502   ~5%    {2} r7 = JOIN r6 WITH Files#a547fcb4::Location::getStartLine#0#dispred#ff ON FIRST 1 OUTPUT Lhs.0, (Lhs.1 ++ ":" ++ toString(Rhs.1))
                     
        2278502   ~5%    {2} r8 = r3 UNION r7
        2278502   ~5%    {2} r9 = r1 UNION r8
                         return r9

[2023-06-05 10:48:09] Evaluated non-recursive predicate project#Files#a547fcb4::Location::toString#0#dispred#ff@68e576a6 in 54ms (size: 2278502).
Evaluated relational algebra for predicate project#Files#a547fcb4::Location::toString#0#dispred#ff@68e576a6 with tuple counts:
        2278502  ~0%    {1} r1 = SCAN Files#a547fcb4::Location::toString#0#dispred#ff OUTPUT In.0
        2278502  ~0%    {1} r2 = STREAM DEDUP r1
                        return r2

[tausbn]

Thanks! I wonder why we did it this way in the first place.
Just one of life's little mysteries, I guess.