gh-38254: Extend the method get_knotinfo of the Link class to cover non-prime knots
    
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This PR implements a task from the following code-comment in `link.py`:

>        # ToDo: extension to non prime links in which case an element
of the monoid
>        # over :class:`KnotInfo` should be returned

In connection with this I switch the output of `get_knotinfo` to
elements of the new class `FreeKnotInfoMonoid` for all knots (prime or
not) For multi-component links I keep the output as it is, since the
`FreeKnotInfoMonoid` does not make sence here.

Another thing changes: Currently, if the `unique=False` option is used
symmetry mutants may be listed separately, even though they are known to
be isotopic because their symmetry type is reversible or amphicheiral.
Now, if symmetry mutants are known to be isotopic because of their
symmetry type, just the minimal of them is listed (in the order of the
enum).


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preview.

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URL: #38254
Reported by: Sebastian Oehms
Reviewer(s): Sebastian Oehms, Travis Scrimshaw

Author: Release Manager

src/doc/en/reference/knots/index.rst

@@ -7,5 +7,6 @@ Knot Theory
    sage/knots/knot
    sage/knots/link
    sage/knots/knotinfo
+   sage/knots/free_knotinfo_monoid
 
 .. include:: ../footer.txt

src/sage/databases/knotinfo_db.py

@@ -793,7 +793,7 @@ def _test_database(self, **options):
 
             sage: from sage.databases.knotinfo_db import KnotInfoDataBase
             sage: ki_db = KnotInfoDataBase()
-            sage: TestSuite(ki_db).run()    # long time indirect doctest
+            sage: TestSuite(ki_db).run()    # optional - database_knotinfo, long time, indirect doctest
         """
         from sage.knots.knotinfo import KnotInfo
         from sage.misc.misc import some_tuples

src/sage/knots/all.py

@@ -1,5 +1,4 @@
 from sage.misc.lazy_import import lazy_import
-from sage.features.databases import DatabaseKnotInfo
 
 lazy_import('sage.knots.knot', ['Knot', 'Knots'])
 lazy_import('sage.knots.link', 'Link')