[text selection] Add the whitespaces present in the pdf in the text chunk

- it aims to fix issue #14627;
- the basic idea of the recent text refactoring was to only consider the rendered visible whitespaces.
  But sometimes, the heuristics aren't correct and although some whitespaces are in the text stream
  they weren't in the text chunks because they were too small. Hence we added some exceptions, for example,
  we always add a whitespace when it is between two non-whitespace chars but only when in the same Tj.
  So basically, this patch removes the constraint to have the chars in the same Tj
  (in using a circular buffer to save the two last chars) but don't add a space when the visible space is really
  too small (hence `NOT_A_SPACE_FACTOR`).

test/pdfs/.gitignore

@@ -515,3 +515,4 @@
 !issue14497.pdf
 !issue14502.pdf
 !issue13211.pdf
+!issue14627.pdf

test/test_manifest.json

@@ -6329,5 +6329,11 @@
       "md5": "d193853e8a123dc50eeea593a4150b60",
       "rounds": 1,
       "type": "eq"
+   },
+   {  "id": "issue14627",
+      "file": "pdfs/issue14627.pdf",
+      "md5": "5d1bfcc3b3130bfa7e33e43990e2213a",
+      "rounds": 1,
+      "type": "text"
    }
 ]

test/unit/api_spec.js

@@ -1999,7 +1999,7 @@ describe("api", function () {
       const data = await Promise.all([defaultPromise, parametersPromise]);
 
       expect(!!data[0].items).toEqual(true);
-      expect(data[0].items.length).toEqual(11);
+      expect(data[0].items.length).toEqual(15);
       expect(!!data[0].styles).toEqual(true);
 
       const page1 = mergeText(data[0].items);

test/unit/pdf_find_controller_spec.js

@@ -579,14 +579,14 @@ describe("pdf_find_controller", function () {
       },
       pageMatches: [
         [
-          299, 337, 414, 476, 623, 797, 978, 984, 1010, 1058, 1079, 1144, 1152,
-          1274, 1343, 1391, 1399, 1421, 1497, 1521, 1527, 1684, 1774, 1786,
-          1857, 1879, 1909, 1946, 2064, 2074, 2161, 2178, 2213, 2227, 2272,
-          2322, 2359, 2401, 2412, 2423, 2462, 2532, 2538, 2553, 2562, 2576,
-          2602, 2613, 2638, 2668, 2792, 2805, 2836, 2848, 2859, 2896, 2902,
-          2916, 2940, 2960, 3091, 3239, 3249, 3339, 3387, 3394, 3468, 3477,
-          3485, 3502, 3690, 3696, 3711, 3758, 3789, 3865, 3977, 4052, 4058,
-          4071,
+          302, 340, 418, 481, 628, 802, 983, 989, 1015, 1063, 1084, 1149, 1157,
+          1278, 1346, 1394, 1402, 1424, 1500, 1524, 1530, 1686, 1776, 1788,
+          1859, 1881, 1911, 1948, 2066, 2076, 2163, 2180, 2215, 2229, 2274,
+          2324, 2360, 2402, 2413, 2424, 2463, 2532, 2538, 2553, 2562, 2576,
+          2602, 2613, 2638, 2668, 2792, 2805, 2836, 2847, 2858, 2895, 2901,
+          2915, 2939, 2959, 3089, 3236, 3246, 3336, 3384, 3391, 3465, 3474,
+          3482, 3499, 3687, 3693, 3708, 3755, 3786, 3862, 3974, 4049, 4055,
+          4068,
         ],
       ],
       pageMatchesLength: [