Add APIs to report FreeType features

[akx]

Refs #9898 (part of the investigation there).

This PR adds new PIL.features APIs to introspect the FreeType features that are available for a given build. On my default macOS-Homebrew-supplied-FreeType, the features are

FreeType built with bytecode_interpreter, bzip2, color_layers, lzw, mac_fonts, png, subpixel_hinting, svg, zlib

but when FreeType is built as an everything-and-the-kitchen-sink build,

FreeType built with brotli, bytecode_interpreter, bzip2, color_layers, gpos_kerning, harfbuzz_autohinter, lzw, mac_fonts, png, subpixel_hinting, svg, zlib

The existence of gpos_kerning here (and not in the default build) is the interesting thing for #9898, as it looks like Noto Sans doesn't have a kern table, just GPOS (though that'll only matter if one explicitly requests basic layout):

$ uvx --from=fonttools[lxml] ttx Tests/fonts/NotoSans-Regular.ttf 2>&1 | grep kern
$ uvx --from=fonttools[lxml] ttx Tests/fonts/NotoSans-Regular.ttf 2>&1 | grep GPOS
Dumping 'GPOS' table...
~/b/Pillow (ft-features) $

Let's see what the flags end up being on the CI builds.

[akx]

#	Checks	FreeType built with
1 (21)	Benchmark Python 3.14 Docs debian-13-trixie-amd64 debian-13-trixie-x86 ubuntu-24.04-noble-amd64 ubuntu-24.04-noble-amd64-valgrind 1, 2, 3, 4 ubuntu-latest Python 3.11, 3.12, 3.13, 3.14, 3.14t, 3.15, 3.15t, pypy3.11	brotli, bytecode_interpreter, bzip2, color_layers, lzw, mac_fonts, png, subpixel_hinting, svg, zlib
2 (11)	MinGW alpine amazon-2023-amd64 arch centos-stream-10-amd64 fedora-43-amd64 fedora-44-amd64 ubuntu-26.04-resolute-amd64 ubuntu-26.04-resolute-arm64v8 ubuntu-26.04-resolute-ppc64le ubuntu-26.04-resolute-s390x	brotli, bytecode_interpreter, bzip2, color_layers, harfbuzz_autohinter, lzw, mac_fonts, png, subpixel_hinting, svg, zlib
3 (8)	macos-26-intel Python 3.11 macos-latest Python 3.12, 3.13, 3.14, 3.14t, 3.15, 3.15t, pypy3.11	bytecode_interpreter, bzip2, color_layers, lzw, mac_fonts, png, subpixel_hinting, svg, zlib
4 (6)	Python 3.11 (x86) Python 3.12 (x64) Python 3.13 (x64) Python 3.14 (x64) Python 3.15 (x64) Python pypy3.11 (x64)	bytecode_interpreter, color_layers, lzw, mac_fonts, subpixel_hinting, svg, zlib
5 (1)	centos-stream-9-amd64	brotli, bytecode_interpreter, bzip2, color_layers, lzw, mac_fonts, subpixel_hinting, svg
6 (1)	gentoo	bytecode_interpreter, bzip2, color_layers, harfbuzz_autohinter, lzw, mac_fonts, png, subpixel_hinting, svg, zlib

Differences at a glance

Feature	G1	G2	G3	G4	G5	G6
brotli	✅	✅	—	—	✅	—
bytecode_interpreter	✅	✅	✅	✅	✅	✅
bzip2	✅	✅	✅	—	✅	✅
color_layers	✅	✅	✅	✅	✅	✅
harfbuzz_autohinter	—	✅	—	—	—	✅
lzw	✅	✅	✅	✅	✅	✅
mac_fonts	✅	✅	✅	✅	✅	✅
png	✅	✅	✅	—	—	✅
subpixel_hinting	✅	✅	✅	✅	✅	✅
svg	✅	✅	✅	✅	✅	✅
zlib	✅	✅	✅	✅	—	✅

So yeah, no build of ours seems to enable gpos_kerning, so the only way to get kerning for fonts with a GPOS table is RAQM shaping.