Trivial simplifications for arccos

[rhinopotamus]

This fixes a couple of places where arccos doesn't automatically simplify for ratios arising from the unit circle (but arcsin does).

Turns out that in src/sage/symbolic/ginac/inifcns_trig.cpp, asin_eval has some logic handling unit circle cases directly that was not replicated in acos_eval. I copy-pasted the logic from asin_eval and modified appropriately.

Partially fixes #24211.

I'm not sure exactly how to create tests covering this change but would be happy to do so with a little guidance!

📝 Checklist

• The title is concise, informative, and self-explanatory.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

None!

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[tscrim]

You should be able to add doctests showing the simplifications are occurring in the output. I imagine

sage: arcsin(sqrt(2)/2)
1/4*pi
sage: arccos(sqrt(2)/2)  # is simplified to 1/4*pi with your change
arccos(1/2*sqrt(2))

[fchapoton]

one test has to be fixed:

File "src/doc/de/thematische_anleitungen/sage_gymnasium.rst", line 790, in doc.de.thematische_anleitungen.sage_gymnasium
Failed example:
    acos(sqrt(3)/2)
Expected:
    arccos(1/2*sqrt(3))
Got:
    1/6*pi

and the same in src/sage/tests/books/computational-mathematics-with-sagemath/premierspas_doctest.py