port improved overflow resolution patch from hb-repacker

via @garretrieger, there's been a patch to hb-repacker that we will want to port. the PR is at https://github.com/harfbuzz/harfbuzz/pull/4517.

From chat,

> To reproduce the original issue I ran into:
hb-subset GoogleSansMyanmar\[opsz\,wght\].ttf --unicodes="0x1000,0x1001,0x1002,0x1003,0x1004,0x1005,0x1006,0x1007,0x1008,0x1009,0x100A,0x100B,0x100C,0x100D,0x100E,0x100F,0x1010,0x1011,0x1012,0x1013,0x1014,0x1015,0x1016,0x1017,0x1018,0x1019,0x101A,0x101B,0x101C,0x101D,0x101E,0x101F,0x1020,0x1021,0x1022,0x1023,0x1024,0x1025,0x1026,0x1027,0x1028,0x1029,0x102A,0x102B,0x102C,0x102D,0x102E,0x102F,0x1030,0x1031,0x1032,0x1033,0x1034,0x1035,0x1036,0x1037,0x1038,0x1039,0x103A,0x103B,0x103C,0x103D,0x103E,0x103F,0x1040,0x1041,0x1042,0x1043,0x1044,0x1045,0x1046,0x1047,0x1048,0x1049,0x104A,0x104B,0x104C,0x104D,0x104E,0x104F,0x1050,0x1051,0x1052,0x1053,0x1054,0x1055,0x1056,0x1057,0x1058,0x1059,0x105A,0x105B,0x105C,0x105D,0x105E,0x105F,0x1060,0x1061,0x1062,0x1063,0x1064,0x1065,0x1066,0x1067,0x1068,0x1069,0x106A,0x106B,0x106C,0x106D,0x106E,0x106F,0x1070,0x1071,0x1072,0x1073,0x1074,0x1075,0x1076,0x1077,0x1078,0x1079,0x107A,0x107B,0x107C,0x107D,0x107E,0x107F,0x1080,0x1081,0x1082,0x1083,0x1084,0x1085,0x1086,0x1087,0x1088,0x1089,0x108A,0x108B,0x108C,0x108D,0x108E,0x108F,0x1090,0x1091,0x1092,0x1093,0x1094,0x1095,0x1096,0x1097,0x1098,0x1099,0x109A,0x109B,0x109C,0x109D,0x109E,0x109F,0x200B,0x200C,0x200D,0x25CC,0xA9E0,0xA9E1,0xA9E2,0xA9E3,0xA9E4,0xA9E5,0xA9E6,0xA9E7,0xA9E8,0xA9E9,0xA9EA,0xA9EB,0xA9EC,0xA9ED,0xA9EE,0xA9EF,0xA9F0,0xA9F1,0xA9F2,0xA9F3,0xA9F4,0xA9F5,0xA9F6,0xA9F7,0xA9F8,0xA9F9,0xA9FA,0xA9FB,0xA9FC,0xA9FD,0xA9FE,0xAA60,0xAA61,0xAA62,0xAA63,0xAA64,0xAA65,0xAA66,0xAA67,0xAA68,0xAA69,0xAA6A,0xAA6B,0xAA6C,0xAA6D,0xAA6E,0xAA6F,0xAA70,0xAA71,0xAA72,0xAA73,0xAA74,0xAA75,0xAA76,0xAA77,0xAA78,0xAA79,0xAA7A,0xAA7B,0xAA7C,0xAA7D,0xAA7E,0xAA7F,0x0000,0x000D,0x0020,0x0021,0x0022,0x0023,0x0024,0x0025,0x0026,0x0027,0x0028,0x0029,0x002A,0x002B,0x002C,0x002D,0x002E,0x002F,0x0030,0x0031,0x0032,0x0033,0x0034,0x0035,0x0036,0x0037,0x0038,0x0039,0x003A,0x003B,0x003C,0x003D,0x003E,0x003F,0x0040,0x0041,0x0042,0x0043,0x0044,0x0045,0x0046,0x0047,0x0048,0x0049,0x004A,0x004B,0x004C,0x004D,0x004E,0x004F,0x0050,0x0051,0x0052,0x0053,0x0054,0x0055,0x0056,0x0057,0x0058,0x0059,0x005A,0x005B,0x005C,0x005D,0x005E,0x005F,0x0060,0x0061,0x0062,0x0063,0x0064,0x0065,0x0066,0x0067,0x0068,0x0069,0x006A,0x006B,0x006C,0x006D,0x006E,0x006F,0x0070,0x0071,0x0072,0x0073,0x0074,0x0075,0x0076,0x0077,0x0078,0x0079,0x007A,0x007B,0x007C,0x007D,0x007E,0x00A0,0x00A1,0x00A2,0x00A3,0x00A4,0x00A5,0x00A6,0x00A7,0x00A8,0x00A9,0x00AA,0x00AB,0x00AC,0x00AD,0x00AE,0x00AF,0x00B0,0x00B1,0x00B2,0x00B3,0x00B4,0x00B5,0x00B6,0x00B7,0x00B8,0x00B9,0x00BA,0x00BB,0x00BC,0x00BD,0x00BE,0x00BF,0x00C0,0x00C1,0x00C2,0x00C3,0x00C4,0x00C5,0x00C6,0x00C7,0x00C8,0x00C9,0x00CA,0x00CB,0x00CC,0x00CD,0x00CE,0x00CF,0x00D0,0x00D1,0x00D2,0x00D3,0x00D4,0x00D5,0x00D6,0x00D7,0x00D8,0x00D9,0x00DA,0x00DB,0x00DC,0x00DD,0x00DE,0x00DF,0x00E0,0x00E1,0x00E2,0x00E3,0x00E4,0x00E5,0x00E6,0x00E7,0x00E8,0x00E9,0x00EA,0x00EB,0x00EC,0x00ED,0x00EE,0x00EF,0x00F0,0x00F1,0x00F2,0x00F3,0x00F4,0x00F5,0x00F6,0x00F7,0x00F8,0x00F9,0x00FA,0x00FB,0x00FC,0x00FD,0x00FE,0x00FF,0x0131,0x0152,0x0153,0x02BB,0x02BC,0x02C6,0x02DA,0x02DC,0x0300,0x0301,0x0303,0x0304,0x0308,0x0309,0x0323,0x0329,0x2002,0x200B,0x2009,0x2013,0x2014,0x2018,0x2019,0x201A,0x201C,0x201D,0x201E,0x2022,0x2026,0x2032,0x2033,0x2039,0x203A,0x2044,0x2074,0x20AC,0x2122,0x2191,0x2193,0x2212,0x2215,0xFEFF,0xFFFD" --instance="wght=400" --output-file=output.ttf

which resulted in a graph that hb was failing to pack.

Start by reviewing the improved overflow-resolution patch in harfbuzz PR #4517 and reproduce the failure with the provided hb-subset command using GoogleSansMyanmar. Trace where the resulting graph fails to pack, then port the patch into fontations and verify that the reproduced graph packs successfully.

Written by the indexing model from the issue text.