Tr/VCS: Fix various issues with translations

Inserting the name for the "commit" operation into messages relies on a
certain sentence structure and doesn't work with translations. Same for
"optional" error messages. Use different complete messages for the
different cases instead.

Avoid explicit line endings, use automatic word wrap instead.

Add some quotes and full stops.

Fix message with plural.

Don't use %n for constant number (inline in message with assert).

Improve confusing tool tip for instant blame.

Change-Id: Ic8453763279753ebd5898858951acddcf311e6e4
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/git/gitclient.cpp

@@ -2873,7 +2873,7 @@ bool GitClient::addAndCommit(const FilePath &repositoryDirectory,
         GitPlugin::updateCurrentBranch();
         return true;
     }
-    VcsOutputWindow::appendError(Tr::tr("Cannot commit %n files", nullptr, commitCount) + "\n");
+    VcsOutputWindow::appendError(Tr::tr("Cannot commit %n file(s)", nullptr, commitCount) + "\n");
     return false;
 }