improve parser recovery if keyword is used as named parameter (PY-8318)

python/testData/psi/KeywordAsNamedParameter.py

@@ -0,0 +1,2 @@
+def f(from=1, another_one=2):
+    pass

python/testData/psi/KeywordAsNamedParameter.txt

@@ -0,0 +1,24 @@
+PyFile:KeywordAsNamedParameter.py
+  PyFunction('f')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('f')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PsiErrorElement:formal parameter name expected
+        PsiElement(Py:FROM_KEYWORD)('from')
+        PsiElement(Py:EQ)('=')
+        PsiElement(Py:INTEGER_LITERAL)('1')
+      PsiElement(Py:COMMA)(',')
+      PsiWhiteSpace(' ')
+      PyNamedParameter('another_one')
+        PsiElement(Py:IDENTIFIER)('another_one')
+        PsiElement(Py:EQ)('=')
+        PyNumericLiteralExpression
+          PsiElement(Py:INTEGER_LITERAL)('2')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyPassStatement
+        PsiElement(Py:PASS_KEYWORD)('pass')