[SPARK-50147][PYTHON][DOCS][TESTS] Refine docstring for trigonometric…

… functions

### What changes were proposed in this pull request?
Refine docstring for trigonometric functions

### Why are the changes needed?
1, make example copy-pasteable;
2, clarify str is a column name or literal string;
3, show both the input columns and output columns, to make the projection more clear;
4, improve the test coverage by adding more doctests;

### Does this PR introduce _any_ user-facing change?
doc changes

### How was this patch tested?
added doctests

### Was this patch authored or co-authored using generative AI tooling?
no

Closes #48678 from zhengruifeng/py_doc_2.

Authored-by: Ruifeng Zheng <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>