PY-8989 Support raw strings in "Convert triple-quoted to single-quoted" intention

python/testData/intentions/ConvertTripleQuotedStringIsNotAvailableForRawStrings.py

@@ -1,2 +0,0 @@
-S = r"""foo<caret>
-bar"""

python/testData/intentions/afterConvertTripleQuotedStringRawStrings.py

@@ -0,0 +1,6 @@
+S = (r'foo' '\n'
+     r'double-only"' '\n'
+     r"single-only'" '\n'
+     r"mix'ed" r'"' '\n'
+     "\r\n"
+     r'one line')

python/testData/intentions/beforeConvertTripleQuotedStringRawStrings.py

@@ -0,0 +1,7 @@
+S = (<caret>r'''foo
+double-only"
+single-only'
+mix'ed"
+'''
+"""\r\n"""
+r'one line')