refactor: improved core barrel exports and Application class (#10286)

BREAKING CHANGES:

`Application.orientation` is no longer a function.

Migration: Remove `()` from the `Application.orientation()` call:
```diff
import { Application } from "@nativescript/core";

-console.log(Application.orientation());
+console.log(Application.orientation);
```


`Application.systemAppearance` is no longer a function.

Migration: Remove `()` from the `Application.systemAppearance()` call:
```diff
import { Application } from "@nativescript/core";

-console.log(Application.systemAppearance());
+console.log(Application.systemAppearance);
```

packages/core/utils/android/index.ts

@@ -0,0 +1,171 @@
+import { Application } from '../../application';
+import { Trace } from '../../trace';
+
+let application: android.app.Application;
+let applicationContext: android.content.Context;
+let contextResources: android.content.res.Resources;
+let packageName: string;
+
+export function getApplicationContext() {
+	if (!applicationContext) {
+		applicationContext = getApplication().getApplicationContext();
+	}
+
+	return applicationContext;
+}
+export function getCurrentActivity() {
+	if (!Application) {
+		return null;
+	}
+	return Application.android.foregroundActivity || Application.android.startActivity;
+}
+export function getApplication() {
+	if (!application) {
+		application = Application.android.getNativeApplication();
+	}
+
+	return application;
+}
+export function getResources() {
+	if (!contextResources) {
+		contextResources = getApplication().getResources();
+	}
+
+	return contextResources;
+}
+export function getPackageName() {
+	if (!packageName) {
+		packageName = getApplicationContext().getPackageName();
+	}
+
+	return packageName;
+}
+
+let inputMethodManager: android.view.inputmethod.InputMethodManager;
+export function getInputMethodManager(): android.view.inputmethod.InputMethodManager {
+	if (!inputMethodManager) {
+		inputMethodManager = <android.view.inputmethod.InputMethodManager>getApplicationContext().getSystemService(android.content.Context.INPUT_METHOD_SERVICE);
+	}
+
+	return inputMethodManager;
+}
+
+export function showSoftInput(nativeView: android.view.View): void {
+	const inputManager = getInputMethodManager();
+	if (inputManager && nativeView instanceof android.view.View) {
+		inputManager.showSoftInput(nativeView, android.view.inputmethod.InputMethodManager.SHOW_IMPLICIT);
+	}
+}
+
+export function dismissSoftInput(nativeView?: android.view.View): void {
+	const inputManager = getInputMethodManager();
+	let windowToken: android.os.IBinder;
+
+	if (nativeView instanceof android.view.View) {
+		if (!nativeView.hasFocus()) {
+			return;
+		}
+		windowToken = nativeView.getWindowToken();
+	} else if (getCurrentActivity() instanceof androidx.appcompat.app.AppCompatActivity) {
+		const decorView = getCurrentActivity().getWindow().getDecorView();
+		if (decorView) {
+			windowToken = decorView.getWindowToken();
+			decorView.requestFocus();
+		} else {
+			windowToken = null;
+		}
+	}
+
+	if (inputManager && windowToken) {
+		inputManager.hideSoftInputFromWindow(windowToken, 0);
+	}
+}
+
+export namespace collections {
+	export function stringArrayToStringSet(str: string[]): java.util.HashSet<string> {
+		const hashSet = new java.util.HashSet<string>();
+		if (str !== undefined) {
+			for (const element in str) {
+				hashSet.add('' + str[element]);
+			}
+		}
+
+		return hashSet;
+	}
+
+	export function stringSetToStringArray(stringSet: any): string[] {
+		const arr = [];
+		if (stringSet !== undefined) {
+			const it = stringSet.iterator();
+			while (it.hasNext()) {
+				const element = '' + it.next();
+				arr.push(element);
+			}
+		}
+
+		return arr;
+	}
+}
+
+export namespace resources {
+	let attr;
+	const attrCache = new Map<string, number>();
+
+	export function getDrawableId(name) {
+		return getId(':drawable/' + name);
+	}
+
+	export function getStringId(name) {
+		return getId(':string/' + name);
+	}
+
+	export function getId(name: string): number {
+		const resources = getResources();
+		const packageName = getPackageName();
+		const uri = packageName + name;
+
+		return resources.getIdentifier(uri, null, null);
+	}
+	export function getResource(name: string, type?: string): number {
+		return getResources().getIdentifier(name, type, getPackageName());
+	}
+	export function getPalleteColor(name: string, context: android.content.Context): number {
+		return getPaletteColor(name, context);
+	}
+	export function getPaletteColor(name: string, context: android.content.Context): number {
+		if (attrCache.has(name)) {
+			return attrCache.get(name);
+		}
+
+		let result = 0;
+		try {
+			if (!attr) {
+				attr = java.lang.Class.forName('androidx.appcompat.R$attr');
+			}
+
+			let colorID = 0;
+			const field = attr.getField(name);
+			if (field) {
+				colorID = field.getInt(null);
+			}
+
+			if (colorID) {
+				const typedValue = new android.util.TypedValue();
+				context.getTheme().resolveAttribute(colorID, typedValue, true);
+				result = typedValue.data;
+			}
+		} catch (ex) {
+			Trace.write('Cannot get pallete color: ' + name, Trace.categories.Error, Trace.messageType.error);
+		}
+
+		attrCache.set(name, result);
+
+		return result;
+	}
+}
+
+export function isRealDevice(): boolean {
+	const fingerprint = android.os.Build.FINGERPRINT;
+
+	return fingerprint != null && (fingerprint.indexOf('vbox') > -1 || fingerprint.indexOf('generic') > -1);
+}