Add a warning to chplcheck for confusing indentation (chapel-lang#23667)

This PR adds a warning to the Chapel linter for "misleading
indentation". Misleading indentation occurs when a non-curly-brace block
is used in a for loop or if-else statement, but a line of code
underneath is indented to the same extent. For example:

```Chapel
for i in 1..10 do
  writeln("Hello, ");
  writeln("World!");
```

The issue with the above code is that it _looks_ like both statements
are a part of the loop; the user might have even intended that. However,
the syntax of the `do` keyword is that only the statement following it
is part of the block; thus, the code printing `World` is not run in a
loop. Thus, the way the code _looks_ (and might be written in an
indentation-sensitive language like Python) is not how it actually
behaves.

```
➜  chapel git:(confusing-indentation) cat good.chpl
for i in 1..10 do
    writeln("Hello!");
writeln("World!");
➜  chapel git:(confusing-indentation) python3 tools/chapel-py/chplcheck.py good.chpl
➜  chapel git:(confusing-indentation) cat bad.chpl
for i in 1..10 do
    writeln("Hello!");
    writeln("World!");
➜  chapel git:(confusing-indentation) python3 tools/chapel-py/chplcheck.py bad.chpl
bad.chpl:3: node violates rule MisleadingIndentation
```

Reviewed by @jabraham17 -- thanks!

tools/chapel-py/chplcheck.py

@@ -20,6 +20,7 @@
 
 import chapel
 import chapel.core
+import chapel.replace
 import re
 import sys
 import argparse
@@ -134,6 +135,20 @@ def check_reserved_prefix(node):
 def check_redundant_block(node):
     return node.block_style() != "unnecessary"
 
+def check_misleading_indentation(node):
+    prev = None
+    for child in node:
+        yield from check_misleading_indentation(child)
+
+        if prev is not None:
+            if child.location().start()[1] == prev.location().start()[1]:
+                yield child
+
+        if isinstance(child, chapel.core.Loop) and child.block_style() == "implicit":
+            grandchildren = list(child)
+            if len(grandchildren) > 0:
+                prev = list(grandchildren[-1])[0]
+
 Rules = [
     ("CamelCaseVariables", chapel.core.VarLikeDecl, check_camel_case_var),
     ("CamelCaseRecords", chapel.core.Record, check_camel_case),
@@ -162,5 +177,8 @@ def main():
     for group in consecutive_decls(ast):
         report_violation(group[1], "ConsecutiveDecls")
 
+    for node in check_misleading_indentation(ast):
+        report_violation(node, "MisleadingIndentation")
+
 if __name__ == "__main__":
     main()