Miscellaneous fixes in Python/suggestions.c

[serhiy-storchaka]

• PyDict_GetItem() and PyObject_HasAttr() suppress arbitrary errors and
  should not be used.
• PyUnicode_CompareWithASCIIString() only works if the second argument
  is ASCII string.
• Refleak in get_suggestions_for_name_error.
• Use of borrowed pointer after possible freeing (self).
• Add some missing error checks.

Linked PRs

• gh-106030: Miscellaneous fixes in Python/suggestions.c #106031
• [3.12] gh-106030: Miscellaneous fixes in Python/suggestions.c (GH-106031) #106036
• [3.11] gh-106030: Miscellaneous fixes in Python/suggestions.c (GH-106… #106039