Fix #4461 Dacpac: Extract lets me save to invalid file path like 'sd' and never adds .dacpac / .bacpac (#6424)

* check for valid path

* add unit tests

* bump package version

* addressing comments

extensions/dacpac/src/wizard/pages/extractConfigPage.ts

@@ -55,6 +55,11 @@ export class ExtractConfigPage extends DacFxConfigPage {
 		return r1 && r2;
 	}
 
+	async onPageLeave(): Promise<boolean> {
+		this.appendFileExtensionIfNeeded();
+		return true;
+	}
+
 	public setupNavigationValidator() {
 		this.instance.registerNavigationValidator(() => {
 			if (this.databaseLoader.loading) {