[FL-3055] Getter for application data path (#2181)

* Threads: application id
* Unit tests: appsdata getter test
* Unit tests: moar test cases for appsdata getter
* Unit tests: remove folders after test
* Storage: dir_is_exist, migrate, + unit_tests
* Plugins: migration
* Storage: common_exists, moar unit_tests 4 "common_migrate", "common_migrate" and "common_merge" bugfixes
* Storage: use FuriString for path handling
* Storage API: send caller thread id with path
* Storage: remove StorageType field in storage file list
* Storage: simplify processing
* Storage API: send caller thread id with path everywhere
* Storage: /app alias, unit tests and path creation
* Storage, path helper: remove unused
* Examples: app data example
* App plugins: use new VFS path
* Storage: file_info_is_dir
* Services: handle alias if the service accepts a path.
* App plugins: fixes
* Make PVS happy
* Storage: fix storage_merge_recursive
* Storage: rename process_aliases to resolve_path. Rename APPS_DATA to APP_DATA.
* Apps: use predefined macro instead of raw paths. Example Apps Data: README fixes.
* Storage: rename storage_common_resolve_path to storage_common_resolve_path_and_ensure_app_directory
* Api: fix version
* Storage: rename alias message
* Storage: do not create app folders in path resolving process in certain cases.

---------

Co-authored-by: Astra <93453568+Astrrra@users.noreply.github.com>
Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/examples/example_apps_data/README.md

@@ -0,0 +1,18 @@
+# Apps Data folder Example
+
+This example demonstrates how to utilize the Apps Data folder to store data that is not part of the app itself, such as user data, configuration files, and so forth.
+
+## What is the Apps Data Folder?
+
+The **Apps Data** folder is a folder used to store data for external apps that are not part of the main firmware. 
+
+The path to the current application folder is related to the `appid` of the app. The `appid` is used to identify the app in the app store and is stored in the `application.fam` file. 
+The Apps Data folder is located only on the external storage, the SD card.
+
+For example, if the `appid` of the app is `snake_game`, the path to the Apps Data folder will be `/ext/apps_data/snake_game`. But using raw paths is not recommended, because the path to the Apps Data folder can change in the future. Use the `/app` alias instead.
+
+## How to get the path to the Apps Data folder?
+
+You can use `/app` alias to get the path to the current application data folder. For example, if you want to open a file `config.txt` in the Apps Data folder, you can use the next path: `/app/config.txt`. But this way is not recommended, because even the `/app` alias can change in the future.
+
+We recommend to use the `APP_DATA_PATH` macro to get the path to the Apps Data folder. For example, if you want to open a file `config.txt` in the Apps Data folder, you can use the next path: `APP_DATA_PATH("config.txt")`.

applications/examples/example_apps_data/application.fam

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+App(
+    appid="example_apps_data",
+    name="Example: Apps Data",
+    apptype=FlipperAppType.EXTERNAL,
+    entry_point="example_apps_data_main",
+    requires=["gui"],
+    stack_size=1 * 1024,
+    fap_category="Examples",
+)

applications/examples/example_apps_data/example_apps_data.c

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+#include <furi.h>
+#include <storage/storage.h>
+
+// Define log tag
+#define TAG "example_apps_data"
+
+// Application entry point
+int32_t example_apps_data_main(void* p) {
+    // Mark argument as unused
+    UNUSED(p);
+
+    // Open storage
+    Storage* storage = furi_record_open(RECORD_STORAGE);
+
+    // Allocate file
+    File* file = storage_file_alloc(storage);
+
+    // Get the path to the current application data folder
+    // That is: /ext/apps_data/<app_name>
+    // And it will create folders in the path if they don't exist
+    // In this example it will create /ext/apps_data/example_apps_data
+    // And file will be /ext/apps_data/example_apps_data/test.txt
+
+    // Open file, write data and close it
+    if(!storage_file_open(file, APP_DATA_PATH("test.txt"), FSAM_WRITE, FSOM_CREATE_ALWAYS)) {
+        FURI_LOG_E(TAG, "Failed to open file");
+    }
+    if(!storage_file_write(file, "Hello World!", strlen("Hello World!"))) {
+        FURI_LOG_E(TAG, "Failed to write to file");
+    }
+    storage_file_close(file);
+
+    // Deallocate file
+    storage_file_free(file);
+
+    // Close storage
+    furi_record_close(RECORD_STORAGE);
+
+    return 0;
+}