feat(studio): real install progress in the store dialog and the wizard

Both surfaces showed an indeterminate spinner for the whole install,
because the hub only offered a unary call. They now follow
HubAdmin/InstallModuleStream:

- The store's install dialog shows the phase in plain language, the
  overall percentage, megabytes while the size is known, and a seconds
  counter. The counter is the second, independent signal: it keeps
  running even if the hub goes quiet, which is what tells 'slow' apart
  from 'stuck'.
- The setup wizard shows the same bar per module instead of a spinner
  inside the button.
- New strings in both locales for the phases, the byte line and the
  elapsed counter.

progress_bar_visual_test writes the four waiting states to
build/progress/ in either theme, so the result can be judged without
launching the desktop app. Writing it turned up a real trap worth
recording: awaiting toImage() directly in a widget test leaves the
binding waiting forever - the file passed in six seconds, then sat
there until the ten-minute timeout failed the whole suite.
tester.runAsync() is the fix. Full suite: 186 passed.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_localizations.dart

@@ -1982,6 +1982,42 @@ abstract class AppLocalizations {
   /// **'Fetching, verifying, unpacking…'**
   String get storeInstallProgressBody;
 
+  /// No description provided for @installPhaseResolve.
+  ///
+  /// In en, this message translates to:
+  /// **'Looking up the module'**
+  String get installPhaseResolve;
+
+  /// No description provided for @installPhaseDownload.
+  ///
+  /// In en, this message translates to:
+  /// **'Downloading'**
+  String get installPhaseDownload;
+
+  /// No description provided for @installPhaseInstall.
+  ///
+  /// In en, this message translates to:
+  /// **'Verifying and unpacking'**
+  String get installPhaseInstall;
+
+  /// No description provided for @installPhaseDone.
+  ///
+  /// In en, this message translates to:
+  /// **'Done'**
+  String get installPhaseDone;
+
+  /// No description provided for @installBytes.
+  ///
+  /// In en, this message translates to:
+  /// **'{done} of {total} MB'**
+  String installBytes(String done, String total);
+
+  /// No description provided for @installElapsed.
+  ///
+  /// In en, this message translates to:
+  /// **'{seconds} s elapsed'**
+  String installElapsed(int seconds);
+
   /// No description provided for @storeLoadDocs.
   ///
   /// In en, this message translates to: