Update harfbuzz to 2.5.2

[GaryQian]

This updates harfbuzz to the latest version.

Primarily motivated by flutter/flutter#28894, but as harfbuzz is 8 months old as of this PR, this update also picks up plenty of other misc fixes in harfbuzz itself.

[cbracken]

For future archaeologists, please document the reason for needing the update in the commit message.

(I'm assuming this addresses a bug related to emoji size on iOS based on the linked issue)

[cbracken]

This appears to have broken the engine build

[1903/3575] CXX obj/third_party/harfbuzz/src/harfbuzz_sources.hb-common.o
FAILED: obj/third_party/harfbuzz/src/harfbuzz_sources.hb-common.o 
/b/s/w/ir/cache/goma/client/gomacc ../../buildtools/linux-x64/clang/bin/clang++ -MMD -MF obj/third_party/harfbuzz/src/harfbuzz_sources.hb-common.o.d -DHAVE_OT -DHAVE_ICU -DHAVE_ICU_BUILTIN -DUSE_OPENSSL=1 -DUSE_OPENSSL_CERTS=1 -DNO_TCMALLOC -DTOOLCHAIN_VERSION=bac220c15490dcf7b7d8136f75100bbc77e8d217 -DANDROID -DHAVE_SYS_UIO_H -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_FORTIFY_SOURCE=2 -D__compiler_offsetof=__builtin_offsetof -Dnan=__builtin_nan -D__GNU_SOURCE=1 -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_STATIC_IMPLEMENTATION -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -DUCHAR_TYPE=uint16_t -I../.. -Igen -I../../third_party/libcxx/include -I../../third_party/libcxxabi/include -I../../third_party/harfbuzz/src -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -I../../third_party/freetype2/include -fno-strict-aliasing -fPIC -pipe -fcolor-diagnostics -ffunction-sections -funwind-tables -fno-short-enums -nostdinc++ --target=aarch64-linux-android -Wall -Wextra -Wendif-labels -Werror -Wno-missing-field-initializers -Wno-unused-parameter -isystem../../third_party/android_tools/ndk/sources/android/support/include -isystem../../third_party/android_tools/ndk/sysroot/usr/include/aarch64-linux-android -D__ANDROID_API__=22 -fvisibility=hidden --sysroot=/b/s/w/ir/k/src/third_party/android_tools/ndk/sysroot -Wheader-hygiene -Wstring-conversion -Wthread-safety -Oz -fno-ident -fdata-sections -ffunction-sections -fomit-frame-pointer -g2 -Wno-missing-field-initializers -Wno-unused-variable -Wno-sign-compare -Wno-unused-function -Wno-unused-variable -fvisibility-inlines-hidden -std=c++17 -fno-rtti -fno-exceptions   -c ../../third_party/harfbuzz/src/hb-common.cc -o obj/third_party/harfbuzz/src/harfbuzz_sources.hb-common.o
../../third_party/harfbuzz/src/hb-common.cc:75:7: error: comparison of integers of different signs: 'size_t' (aka 'unsigned long') and 'long' [-Werror,-Wsign-compare]
      OPTION ("uniscribe-bug-compatible", uniscribe_bug_compatible);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../third_party/harfbuzz/src/hb-common.cc:73:53: note: expanded from macro 'OPTION'
        if (0 == strncmp (c, name, p - c) && strlen (name) == p - c) do { u.opts.symbol = true; } while (0)
                                             ~~~~~~~~~~~~~ ^  ~~~~~
../../third_party/harfbuzz/src/hb-common.cc:76:7: error: comparison of integers of different signs: 'size_t' (aka 'unsigned long') and 'long' [-Werror,-Wsign-compare]
      OPTION ("aat", aat);
      ^~~~~~~~~~~~~~~~~~~
../../third_party/harfbuzz/src/hb-common.cc:73:53: note: expanded from macro 'OPTION'
        if (0 == strncmp (c, name, p - c) && strlen (name) == p - c) do { u.opts.symbol = true; } while (0)
                                             ~~~~~~~~~~~~~ ^  ~~~~~
2 errors generated.