Always check all Kids nodes, in Catalog.getPageDict, to avoid getting stuck in an empty node further down in the Pages tree (issue 8088)

As discussed on IRC, we need to check all nodes at the *bottom* of the tree to ensure that we find the correct `Page` dict.
Furthermore, this patch also gets rid of the caching present in a previous version, since it's not clear if that really helps.

Note that this patch purposely adds an `eq` test, using a reduced test-case, so that we can be sure that the algorithm actually finds the correct `Page` dict for each `pageIndex`.

Fixes 8088.

test/pdfs/.gitignore

@@ -46,6 +46,7 @@
 !issue7872.pdf
 !issue7901.pdf
 !issue8061.pdf
+!issue8088.pdf
 !bad-PageLabels.pdf
 !filled-background.pdf
 !ArabicCIDTrueType.pdf

test/pdfs/issue8088.pdf

@@ -0,0 +1,163 @@
+%PDF-1.7
+%âãÏÓ
+1 0 obj 
+<<
+/Parent 2 0 R
+/Resources 
+<<
+/Font 
+<<
+/F1 3 0 R
+>>
+>>
+/MediaBox [0 0 200 50]
+/Type /Page
+/Contents 4 0 R
+>>
+endobj 
+4 0 obj 
+<<
+/Length 50
+>>
+stream
+BT
+10 20 TD
+/F1 20 Tf
+(Issue 8088 - Page 2) Tj
+ET
+
+endstream 
+endobj 
+5 0 obj 
+<<
+/Parent 6 0 R
+/Resources 
+<<
+/Font 
+<<
+/F1 3 0 R
+>>
+>>
+/MediaBox [0 0 200 50]
+/Type /Page
+/Contents 7 0 R
+>>
+endobj 
+7 0 obj 
+<<
+/Length 50
+>>
+stream
+BT
+10 20 TD
+/F1 20 Tf
+(Issue 8088 - Page 3) Tj
+ET
+
+endstream 
+endobj 
+8 0 obj 
+<<
+/Parent 9 0 R
+/Kids []
+/Type /Pages
+/Count 0
+>>
+endobj 
+2 0 obj 
+<<
+/Parent 9 0 R
+/Kids [10 0 R 1 0 R]
+/Type /Pages
+/Count 2
+>>
+endobj 
+9 0 obj 
+<<
+/Parent 11 0 R
+/Kids [8 0 R 2 0 R]
+/Type /Pages
+/Count 2
+>>
+endobj 
+6 0 obj 
+<<
+/Parent 11 0 R
+/Kids [5 0 R]
+/Type /Pages
+/Count 1
+>>
+endobj 
+11 0 obj 
+<<
+/Kids [9 0 R 6 0 R]
+/Type /Pages
+/Count 3
+>>
+endobj 
+12 0 obj 
+<<
+/Pages 11 0 R
+/Type /Catalog
+>>
+endobj 
+10 0 obj 
+<<
+/Parent 2 0 R
+/Resources 
+<<
+/Font 
+<<
+/F1 3 0 R
+>>
+>>
+/MediaBox [0 0 200 50]
+/Type /Page
+/Contents 13 0 R
+>>
+endobj 
+13 0 obj 
+<<
+/Length 50
+>>
+stream
+BT
+10 20 TD
+/F1 20 Tf
+(Issue 8088 - Page 1) Tj
+ET
+
+endstream 
+endobj 
+3 0 obj 
+<<
+/BaseFont /Times-Roman
+/Subtype /Type1
+/Encoding /WinAnsiEncoding
+/Type /Font
+>>
+endobj xref
+0 14
+0000000000 65535 f 
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+0000000847 00000 n 
+0000001031 00000 n 
+trailer
+
+<<
+/Root 12 0 R
+/Size 14
+>>
+startxref
+1235
+%%EOF

test/test_manifest.json

@@ -1318,6 +1318,15 @@
        "lastPage": 6,
        "type": "eq"
     },
+    {  "id": "issue8088",
+       "file": "pdfs/issue8088.pdf",
+       "md5": "5bbc33c7433799487518eb0d8094348c",
+       "rounds": 1,
+       "link": false,
+       "firstPage": 1,
+       "lastPage": 3,
+       "type": "eq"
+    },
     {  "id": "bug866395",
        "file": "pdfs/bug866395.pdf",
        "md5": "f03bc77e84637241980b09a0a220f575",