PY-21161 Don't flip quotes inside inlined expressions if it's not necessary

For instance, when inlining single-quoted string inside triple-quoted
string with the same type of quotes.

python/src/com/jetbrains/python/codeInsight/intentions/PyConvertToFStringIntention.java

@@ -148,13 +148,17 @@ public class PyConvertToFStringIntention extends PyBaseIntentionAction {
       // Nest string contain the same type of quote as host string inside, and we cannot escape inside f-string -- retreat
       final String content = info.getContent();
       final char targetSingleQuote = flipQuote(hostQuote);
-      if (content.indexOf(hostQuote) >= 0 || content.indexOf(targetSingleQuote) >= 0) {
+      if (content.indexOf(hostQuote) >= 0) {
         return null;
       }
       if (!info.isTerminated()) {
         return null;
       }
-      if (info.getSingleQuote() == hostQuote) {
+      if (info.getQuote().startsWith(hostInfo.getQuote())) {
+        if (content.indexOf(targetSingleQuote) >= 0) {
+          return null;
+        }
+        
         final String targetQuote = info.getQuote().replace(hostQuote, targetSingleQuote);
         final String stringWithSwappedQuotes = info.getPrefix() + targetQuote + content + targetQuote;
         final PsiElement replaced = literal.replace(generator.createStringLiteralAlreadyEscaped(stringWithSwappedQuotes));

python/testData/intentions/PyConvertToFStringIntentionTest/percentOperatorInlineSingleQuotedStringInsideTripleQuotedString.py

@@ -0,0 +1,3 @@
+'''
+%s
+''' % '"'

python/testData/intentions/PyConvertToFStringIntentionTest/percentOperatorInlineSingleQuotedStringInsideTripleQuotedString_after.py

@@ -0,0 +1,3 @@
+f'''
+{'"'}
+'''

python/testSrc/com/jetbrains/python/intentions/PyConvertToFStringIntentionTest.java

@@ -120,6 +120,10 @@ public class PyConvertToFStringIntentionTest extends PyIntentionTestCase {
     doTest();
   }
 
+  public void testPercentOperatorInlineSingleQuotedStringInsideTripleQuotedString() {
+    doTest();
+  }
+
   public void testExtractItemAndAttributeAccess() {
     assertSameElements(PyConvertToFStringIntention.extractItemsAndAttributes("{0.foo.bar.baz}"), ".foo", ".bar", ".baz");
     assertSameElements(PyConvertToFStringIntention.extractItemsAndAttributes("{0[foo][.!:][}]}"), "[foo]", "[.!:]", "[}]");