Attempt to combine separate beginText/endText sequences in getTextContent (issue 9984)

Please note that while this *improves* issue 9984 slightly (and likely others too), it's not a complete solution.
The remaining issues are related to the, more general, problems with the existing heuristics related to attempting to combine separate text items.

test/pdfs/.gitignore

@@ -72,6 +72,7 @@
 !issue9458.pdf
 !issue9915_reduced.pdf
 !issue9940.pdf
+!issue9984.pdf
 !bad-PageLabels.pdf
 !decodeACSuccessive.pdf
 !filled-background.pdf

test/test_manifest.json

@@ -1352,6 +1352,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue9984-text",
+       "file": "pdfs/issue9984.pdf",
+       "md5": "41be5f1b43f61892978cfc57c74ccf4c",
+       "rounds": 1,
+       "link": false,
+       "type": "text"
+    },
     {  "id": "issue8570",
        "file": "pdfs/issue8570.pdf",
        "md5": "0355731adb72df233eaa10464dcc8c51",