Add support for the /Catalog Base-URI when resolving URLs (issue 14802)

As far as I can tell, this is actually the very first time that we've seen a PDF document with a Base-URI specified in the /Catalog; please refer to the specification:
https://web.archive.org/web/20220309040754if_/https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf#G11.2097122

To simplify the overall implementation, this new parameter is accessed via the existing `BasePdfManager.docBaseUrl`-getter and will thus override any user-specified `docBaseUrl` API-parameter.

test/pdfs/.gitignore

@@ -238,6 +238,7 @@
 !pdfjsbad1586.pdf
 !standard_fonts.pdf
 !freeculture.pdf
+!issue14802.pdf
 !issue6006.pdf
 !pdfkit_compressed.pdf
 !TAMReview.pdf

test/pdfs/issue14802.pdf

@@ -0,0 +1,89 @@
+%PDF-1.7
+%âãÏÓ
+1 0 obj 
+<<
+/Pages 2 0 R
+/URI 
+<<
+/Base (http://example.com/)
+>>
+/Type /Catalog
+>>
+endobj 
+2 0 obj 
+<<
+/Kids [3 0 R]
+/Type /Pages
+/Count 1
+>>
+endobj 
+3 0 obj 
+<<
+/Parent 2 0 R
+/Annots [4 0 R]
+/Resources 
+<<
+/Font 
+<<
+/F1 5 0 R
+>>
+>>
+/MediaBox [0 0 260 50]
+/Type /Page
+/Contents 6 0 R
+>>
+endobj 
+4 0 obj 
+<<
+/Border [0 0 1]
+/Subtype /Link
+/C [0 0 1]
+/A 
+<<
+/URI (./relative_link.txt)
+/Type /Action
+/S /URI
+>>
+/Type /Annot
+/Rect [5 10 250 40]
+>>
+endobj 
+5 0 obj 
+<<
+/BaseFont /Times-Roman
+/Subtype /Type1
+/Type /Font
+/Encoding /WinAnsiEncoding
+>>
+endobj 
+6 0 obj 
+<<
+/Length 81
+>>
+stream
+1 0 0 rg
+BT
+10 20 TD
+/F1 14 Tf
+(A relative link, with a /Catalog Base-URI) Tj
+ET
+
+endstream 
+endobj xref
+0 7
+0000000000 65535 f 
+0000000015 00000 n 
+0000000106 00000 n 
+0000000165 00000 n 
+0000000310 00000 n 
+0000000467 00000 n 
+0000000568 00000 n 
+trailer
+
+<<
+/Root 1 0 R
+/Size 7
+>>
+startxref
+701
+%%EOF

test/test_manifest.json

@@ -2950,6 +2950,14 @@
       "link": true,
       "type": "eq"
     },
+    {  "id": "issue14802",
+       "file": "pdfs/issue14802.pdf",
+       "md5": "c1e774945fee539c7fcfec00b36dd4e6",
+       "rounds": 1,
+       "type": "eq",
+       "annotations": true,
+       "about": "LinkAnnotation with a relative link, and a /Catalog Base-URI."
+    },
     {  "id": "issue1127-text",
        "file": "pdfs/issue1127.pdf",
        "md5": "4fb2be5ffefeafda4ba977de2a1bb4d8",