Inline Expectation Tests: Allow tag[foo bar]

This is partly motivated by the MaD tests which looks much better now in
my opinion.

I also wanted this for testing argument passing. In Python we're
adopting the same argument positions as Ruby has
[here](4f3751dfea/ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowDispatch.qll (L508-L540))

So it would be nice if `arg[keyword foo]=...` was allowed, without
having to transform the `toString()` result of an argument position into
something without a space.

python/ql/test/experimental/meta/MaDTest.qll

@@ -11,7 +11,9 @@ class MadSinkTest extends InlineExpectationsTest {
   MadSinkTest() { this = "MadSinkTest" }
 
   override string getARelevantTag() {
-    exists(string kind | exists(ModelOutput::getASinkNode(kind)) | result = "mad-sink__" + kind)
+    exists(string kind | exists(ModelOutput::getASinkNode(kind)) |
+      result = "mad-sink[" + kind + "]"
+    )
   }
 
   override predicate hasActualResult(Location location, string element, string tag, string value) {
@@ -21,7 +23,7 @@ class MadSinkTest extends InlineExpectationsTest {
       location = sink.getLocation() and
       element = sink.toString() and
       value = prettyNodeForInlineTest(sink) and
-      tag = "mad-sink__" + kind
+      tag = "mad-sink[" + kind + "]"
     )
   }
 }