Separate app-manager and app-framework from WAMR (#3129)

As planned, the app-manager and app-framework are to be migrated to
https://github.com/bytecodealliance/wamr-app-framework.

ps.
https://github.com/bytecodealliance/wasm-micro-runtime/issues/2329
https://github.com/bytecodealliance/wasm-micro-runtime/wiki/TSC-meeting-notes

samples/gui/wasm-apps/decrease/Makefile

@@ -1,29 +0,0 @@
-# Copyright (C) 2019 Intel Corporation.  All rights reserved.
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-CC = /opt/wasi-sdk/bin/clang
-APP_DIR = ${shell pwd}
-IWASM_DIR = $(APP_DIR)/../../../../core/iwasm
-SDK_DIR = $(APP_DIR)/../../../../wamr-sdk/out/gui/app-sdk
-APP_FRAMEWORK_DIR = $(APP_DIR)/../../../../wamr-sdk/out/gui/app-sdk/wamr-app-framework
-DEPS_DIR = $(APP_DIR)/../../../../core/deps
-
-CFLAGS += -O3 \
-    -Wno-int-conversion \
-    -I$(APP_DIR)/src \
-    -I$(APP_FRAMEWORK_DIR)/include \
-    -I${DEPS_DIR}
-
-SRCS += $(APP_DIR)/src/main.c
-
-all:
-	@$(CC) $(CFLAGS) $(SRCS) \
-    --target=wasm32 -O3 -z stack-size=2048 -Wl,--initial-memory=65536 \
-    --sysroot=$(SDK_DIR)/libc-builtin-sysroot       \
-    -L$(APP_FRAMEWORK_DIR)/lib -lapp_framework      \
-    -Wl,--allow-undefined-file=$(SDK_DIR)/libc-builtin-sysroot/share/defined-symbols.txt \
-    -Wl,--strip-all,--no-entry -nostdlib \
-    -Wl,--export=on_init -Wl,--export=on_timer_callback \
-    -Wl,--export=on_widget_event \
-    -Wl,--export=__heap_base,--export=__data_end \
-    -o ui_decrease.wasm