more test

Summary:
Currently, we don't interpret string literal as file paths or buck target outside of buck build rules, but they do appear in a variety of places in the codebase (for instance in constants in [bzl files](https://www.internalfb.com/code/fbsource/[3dabff0fa10b]/fbcode/aim/fbje/handlers/nowa/codegen/buck_macros.bzl?lines=12))

adding test case first, indexing in next diff

Reviewed By: malanka

Differential Revision: D84832445

fbshipit-source-id: a99b73ebddd85b33cd28d62e72f69df4844dbc4c

Author: Philippe Bidinger

glean/glass/test/regression/tests/buck/documentSymbolIndex_my_defs.out

@@ -3,7 +3,7 @@
     {
         "referenced_file_digests": {},
         "revision": "testhash",
-        "size": 7,
+        "size": 8,
         "symbols": {
             "1": [
                 {
@@ -115,6 +115,31 @@
                     "sym": "test/buck/d/buck_project/my_defs.bzl/MY_CONST"
                 }
             ],
+            "20": [
+                {
+                    "attributes": {
+                        "symbolKind": {
+                            "aInteger": 3
+                        },
+                        "symbolLanguage": {
+                            "aInteger": 11
+                        },
+                        "symbolName": {
+                            "aString": "MY_LIST"
+                        },
+                        "symbolParent": {
+                            "aString": "buck_project/my_defs.bzl"
+                        }
+                    },
+                    "range": {
+                        "columnBegin": 1,
+                        "columnEnd": 56,
+                        "lineBegin": 20,
+                        "lineEnd": 20
+                    },
+                    "sym": "test/buck/d/buck_project/my_defs.bzl/MY_LIST"
+                }
+            ],
             "3": [
                 {
                     "attributes": {