sagemathgh-40020: Fixed infinite recursion in trig functions
    
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Fixes sagemath#35696

When the trig functions sin, cos, tan, csc, sec, or cot are provided
with a symbolic input which expands to 0 they would suffer an infinite
recursion error.

This occurred because of a bug in the corresponding sin_eval, cos_eval,
tan_eval, csc_eval, sec_eval, and cot_eval functions defined in
src/sage/symbolic/ginac/inifcns_trig.cpp. These functions perform a
simplification when the real part of the expanded input is 0. This
simplification led to infinite recursion when the expanded input was
exactly equal to 0.

A check has been added to each of these 6 functions which ensures
correct behaviour when the input expands to 0.
Tests have been added to src/sage/functions/trig.py to cover these
changes.

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### ⌛ Dependencies

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URL: sagemath#40020
Reported by: Caleb Van't Land
Reviewer(s):