Compiled symbolic expressions

As mentioned in #107 and %Alpha 1 , symbolic expressions need to be compiled rather than using lambdas to evaluate these during simulation time. This MR contains an implementation of this, using the tinyexpr evaluation engine to compile and evaluate the expressions.

finesse.cyexpr wraps the parts of tinexpr that we need, using a cy_expr struct, then this is used in ElementWorkspace where an array of these structs is created and initialised. Fast evaluation of symbolic parameters is then performed using this array.

A working example is given in playground/symbolics/scan.py.

This struct has also been used to overhaul how symbolic ABCD matrices get evaluated during a simulation. Each relevant ConnectorWorkspace now stores an array of pointers to cy_expr containing the changing symbolic ABCD matrix elements (NULL if not changing). These are evaluated (with direct pointer access) during the update_parameter_values routine of each of these workspaces.

Things to address now (before merging):

• Fix seg fault that seems to be occurring when evaluating changing ABCD matrix elements in beam splitters
• Fix strange bug where te_compile fails on a lens ABCD element expression, e.g: -1.0/itm_lens_f; error in parsing seems to point to end of string for some reason.