Build and cache libhysteria2.so (#4226)

* add submodule apernet/hysteria

* remove libhysteria2 binary from git repo

* libhysteria2.sh

* ignore *.so

.gitignore

@@ -3,5 +3,4 @@
 V2rayNG/app/release/output.json
 .idea/
 .gradle/
-libtun2socks.so
-libhysteria2.so
+*.so