Do not truncate whitespace for multi-line string (microsoft#23977)

Resolves: microsoft#23743

It seems that when people have a multi line string such surrounded by
""" quotes, the white spacing inside the quote is very much intentional,
and so if we detect that they are in such code-block, we would rather
not normalize/truncate the white spaces for that specific code block.

python_files/normalizeSelection.py

@@ -26,6 +26,10 @@ def _get_statements(selection):
     This will remove empty newlines around and within the selection, dedent it,
     and split it using the result of `ast.parse()`.
     """
+    if '"""' in selection or "'''" in selection:
+        yield selection
+        return
+
     # Remove blank lines within the selection to prevent the REPL from thinking the block is finished.
     lines = (line for line in split_lines(selection) if line.strip() != "")
 

src/test/python_files/terminalExec/sample2_normalized_selection.py

@@ -1,7 +1,15 @@
 def add(x, y):
-    """Adds x to y"""
+    """
+
+    Adds x
+    to
+    y
+
+
+    """
     # Some comment
     return x + y
 
 v = add(1, 7)
 print(v)
+

src/test/python_files/terminalExec/sample2_raw.py

@@ -1,7 +1,13 @@
 def add(x, y):
-    """Adds x to y"""
+    """
+
+    Adds x
+    to
+    y
+
+
+    """
     # Some comment
-
     return x + y
 
 v = add(1, 7)