Merge bitcoin/bitcoin#30049: build, test, doc: Temporarily remove Android-related stuff

5deb0b024e build, test, doc: Temporarily remove Android-related stuff (Hennadii Stepanov)

Pull request description:

  Previously, our Android builds were geared towards generating APKs, which relied on Qt. However, after migrating to C++20, compiling for Android became unfeasible due to Qt 5.15's compatibility limitations with NDK only up to r25, which includes an outdated embedded libc++ (see https://github.com/bitcoin/bitcoin/issues/29360).

  All removed stuff will be reinstated after migrating the build system to CMake and upgrading Qt to version 6.x.

  This PR makes possible a clean migration to the CMake-based build system as it removes code, which is not used at this moment.

ACKs for top commit:
  vasild:
    ACK 5deb0b024e
  fanquake:
    ACK 5deb0b024e - given none of this is currently tested/wont compile. Can be revisted in future.

Tree-SHA512: 3bc2ccfe881e11cc1d78c27acd6f1d86cfba86821ef3bb5eca2e80d978fdfa13659ec82284dcaadc507e2394524dea91d4b8f81d0030c1cef9708df8be76bf07

depends/patches/qt/fix_android_jni_static.patch

@@ -1,17 +0,0 @@
---- old/qtbase/src/plugins/platforms/android/androidjnimain.cpp
-+++ new/qtbase/src/plugins/platforms/android/androidjnimain.cpp
-@@ -979,6 +979,14 @@ Q_DECL_EXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void */*reserved*/)
-         __android_log_print(ANDROID_LOG_FATAL, "Qt", "registerNatives failed");
-         return -1;
-     }
-+
-+    const jint ret = QT_PREPEND_NAMESPACE(QtAndroidPrivate::initJNI(vm, env));
-+    if (ret != 0)
-+    {
-+        __android_log_print(ANDROID_LOG_FATAL, "Qt", "initJNI failed");
-+        return ret;
-+    }
-+
-     QWindowSystemInterfacePrivate::TabletEvent::setPlatformSynthesizesMouse(false);
- 
-     m_javaVM = vm;