Improve error passing task IDs as URL parameter in invalid format

Summary:
Maniphest expects the values of the `ids` URL parameter to be integers. Example: http://phorge.localhost/maniphest/?ids=1,2,3,4 to show a list of tasks with those IDs.
When passing monograms instead (`T` prefix, like `T123` instead of `123`), a cryptic message `Expected a numeric scalar or null for %Ld conversion` is shown.

Thus check if `$this->taskIDs` consists of integers only; if not throw a `PhutilSearchQueryCompilerSyntaxException` with an explanatory error message.

Closes T15838

Test Plan: Go to http://phorge.localhost/maniphest/?ids=T1,T2,T3,T4 before and after applying the patch.

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: avivey, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15838

Differential Revision: https://we.phorge.it/D25669

src/applications/maniphest/query/ManiphestTaskQuery.php

@@ -358,6 +358,10 @@ final class ManiphestTaskQuery extends PhabricatorCursorPagedPolicyAwareQuery {
     $where[] = $this->buildOwnerWhereClause($conn);
 
     if ($this->taskIDs !== null) {
+      if (!ctype_digit(implode('', $this->taskIDs))) {
+        throw new PhutilSearchQueryCompilerSyntaxException(
+          pht('Task IDs must be integer numbers.'));
+      }
       $where[] = qsprintf(
         $conn,
         'task.id in (%Ld)',