[KnownFPClass] Add sNaN deductions for `sin`, `cos`, and `tan`

`KnownFPClass::sin`, `KnownFPClass::cos`, and `KnownFPClass::tan` can currently rule out `NaN` when the input is known to be non-`NaN` and finite, but they do not separately propagate knowledge that the input cannot be `sNaN`.

`sin`, `cos`, and `tan` can only return `sNaN` if the input is `sNaN`. For an `sNaN` input, the result may non-deterministically be either `qNaN` or `sNaN`. Therefore, if the input is known not to be `sNaN`, the result can also be known not to be `sNaN`.

The `KnownFPClass::propagateNonSNaN()` helper can be used to perform this deduction.

Tests should be added/updated for the `sin`, `cos`, and `tan` deductions, including cases where the source is known not to be an `sNaN`.

Start by locating the KnownFPClass::sin, KnownFPClass::cos, and KnownFPClass::tan implementations and their existing tests. Read how propagateNonSNaN() is used, then add or update tests covering inputs known not to be sNaN and verify that all three deductions establish the corresponding result property.

Written by the indexing model from the issue text.