Update Android NDK r26 LTS

[yurybura]

Announcements
KitKat (APIs 19 and 20) is no longer supported. The minimum OS supported by the NDK is Lollipop (API level 21).
libc++ has been updated. The NDK's libc++ now comes directly from our LLVM toolchain, so every future LLVM update is also a libc++ update. Future changelogs will not explicitly mention libc++ updates.

Changelog

[yurybura]

Many problems associated with an outdated version of libc++ can be fixed with an update.

[dg0yt]

#31228, or something similar invasive, is required to make vcpkg CI pass.
Cf. #35851 for build results. (Currently with arm64-android switched to dynamic linkage, but this is another story.)

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[bmanga]

@dg0yt is ndk26 working now that your pr has been merged?

[dg0yt]

The general problem with vcpkg_configure_make is resolved.
vcpkg CI isn't updated to NDK r26b. Some ports may need individual tuning because NDK r26 uncovers issues which were previously hidden, at least with the low API level used in vcpkg CI. Cf. #35851 for inspiration.