CephFSDocumentsProvider: basic xdg-style thumbnail support

needs more work on reducing io @ dir listing, and perhaps validations

ceph: upgrade to reef

move to android-ndk-beta

for better c++20 stdlib support, and prepare for moving to reef

ceph: v17.2.6 rebase

link libcephfs-jni java parts instead of copying

README: document new build approach

jni: add libc++_shared.so link as blob into jniLibs

somehow gradle did not pick this up, needed by libboost

TODO: find out how agp deals with lib deps

gradle: wire up ceph

add our ceph fork as a submodule

to be wired up with gradle later

Containerfile: riggings for ghcr

Containerfile: initial work for containerized building

one step forward to finally hook ceph cmake onto gradle?
maybe we still want to ship prebuilts on a build variant for faster
development? idk
or, can we eventually hook every dependencies and stop using aur
contents, which make containerization not really that desired?

update gradle & wrapper

makes gradlew works without bash and which

build: update toolchain, opt-in predictive back

update prebuilts

brief changelog:
ceph v17.2.3, openssl 1.1.1q, ndk r25.b

README: update status, drop WIP flag

while this is not done, it is already useful enough for general cases

DocumentsProvider: set client_dirsize_rbytes=false

update prebuilts

brief changelog:
ceph v17.2.1, with logcat hack, dirsize_rbytes=false performance fix
openssl 1.1.1p

jni: update to quincy

MediaMetadataReader: support audio

DocumentsProvider: add video metadata support