Add different code-paths to {CMap, ToUnicodeMap}.charCodeOf depending on length, since Array.prototype.indexOf can be extremely inefficient for very large arrays (issue 8372)

Fixes 8372.

test/pdfs/.gitignore

@@ -50,6 +50,7 @@
 !issue8061.pdf
 !issue8088.pdf
 !issue8125.pdf
+!issue8372.pdf
 !issue8424.pdf
 !bad-PageLabels.pdf
 !filled-background.pdf

test/pdfs/issue8372.pdf

@@ -0,0 +1,101 @@
+%PDF-1.7
+%âãÏÓ
+1 0 obj 
+<<
+/BaseFont /AdobeHeitiStd-Regular
+/CIDSystemInfo 2 0 R
+/Subtype /CIDFontType2
+/FontDescriptor 3 0 R
+/Type /Font
+>>
+endobj 
+3 0 obj 
+<<
+/FontName /AdobeHeitiStd-Regular
+/StemV 56
+/Ascent 967
+/Flags 32
+/Descent -283
+/ItalicAngle 0
+/FontBBox [-163 -283 1087 967]
+/Type /FontDescriptor
+/CapHeight 763
+>>
+endobj 
+2 0 obj 
+<<
+/Supplement 4
+/Ordering (GB1)
+/Registry (Adobe)
+>>
+endobj 
+4 0 obj 
+<<
+/Pages 5 0 R
+/Type /Catalog
+>>
+endobj 
+5 0 obj 
+<<
+/MediaBox [0 0 200 50]
+/Kids [6 0 R]
+/Count 1
+/Type /Pages
+>>
+endobj 
+6 0 obj 
+<<
+/Parent 5 0 R
+/MediaBox [0 0 200 50]
+/Resources 
+<<
+/Font 
+<<
+/F1 7 0 R
+>>
+>>
+/Contents 8 0 R
+/Type /Page
+>>
+endobj 
+7 0 obj 
+<<
+/DescendantFonts [1 0 R]
+/BaseFont /AdobeHeitiStd-Regular
+/Subtype /Type0
+/Encoding /UniGB-UTF16-H
+/Type /Font
+>>
+endobj 
+8 0 obj 
+<<
+/Length 46
+>>
+stream
+BT
+10 20 TD
+/F1 20 Tf
+[(vî)0.389893(_U)]TJ
+ET
+
+endstream 
+endobj xref
+0 9
+0000000000 65535 f 
+0000000015 00000 n 
+0000000334 00000 n 
+0000000149 00000 n 
+0000000405 00000 n 
+0000000456 00000 n 
+0000000538 00000 n 
+0000000667 00000 n 
+0000000801 00000 n 
+trailer
+
+<<
+/Root 4 0 R
+/Size 9
+>>
+startxref
+899
+%%EOF

test/test_manifest.json

@@ -2125,6 +2125,13 @@
        "link": false,
        "type": "text"
     },
+    {  "id": "issue8372-text",
+       "file": "pdfs/issue8372.pdf",
+       "md5": "b02fb07364dd00ad5044bd259860da97",
+       "rounds": 1,
+       "link": false,
+       "type": "text"
+    },
     {  "id": "bug894572",
        "file": "pdfs/bug894572.pdf",
        "md5": "e54a6b0451939f685ed37e3d46e16158",