Version 3.6.0-149.2.beta

This reverts commit c1976b0.

Reason for revert: It seems this change caused failures on Flutter
HHH bot. Example log can be found at [0]:
```
| lib/src/super_reader/super_reader.dart:615:14: Error: Final field 'showDebugLeaderBounds' is not initialized.
| Try to initialize the field in the declaration or in every constructor.
|   final bool showDebugLeaderBounds;
|              ^^^^^^^^^^^^^^^^^^^^^

```
Looking at the sources it seems that may be related to the
`// ignore: unused_element` analyzer directive:

```
   602	/// A [SuperReaderDocumentLayerBuilder] that builds a [SelectionLeadersDocumentLayer], which positions
   603	/// leader widgets at the base and extent of the user's selection, so that other widgets
   604	/// can position themselves relative to the user's selection.
   605	class _SelectionLeadersDocumentLayerBuilder implements SuperReaderDocumentLayerBuilder {
   606	  const _SelectionLeadersDocumentLayerBuilder({
   607	    required this.links,
   608	    // ignore: unused_element
   609	    this.showDebugLeaderBounds = false,
   610	  });
   611
   612	  /// Collections of [LayerLink]s, which are given to leader widgets that are
   613	  /// positioned at the selection bounds, and around the full selection.
   614	  final SelectionLayerLinks links;
   615
   616	  /// Whether to paint colorful bounds around the leader widgets, for debugging purposes.
   617	  final bool showDebugLeaderBounds;
```

So tentatively reverting this CL.

[0] https://logs.chromium.org/logs/dart/buildbucket/cr-buildbucket/8739650477551803313/+/u/Run_customer_testing_tests/stdout

Original change's description:
> analyzer: separate unused_element_parameter from unused_element
>
> Fixes #49025
>
> This allows users to blanket ignore unused_element_parameter without
> ignoring unused_element. They are reported in distinct situations so it
> is valid to separate them.
>
> Change-Id: I4844a6a0e0a67cd5e37ed8735b1526e174deb950
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/378500
> Reviewed-by: Brian Wilkerson <[email protected]>
> Reviewed-by: Phil Quitslund <[email protected]>
> Commit-Queue: Samuel Rawlins <[email protected]>
> Reviewed-by: Ryan Macnak <[email protected]>

Change-Id: Ibbba75fe56601c7c4b5535c9142cf94c2dd80b91
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/380460
Reviewed-by: Christopher Fujino <[email protected]>
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/380689
Commit-Queue: Kevin Chisholm <[email protected]>

tools/VERSION

@@ -28,4 +28,4 @@ MAJOR 3
 MINOR 6
 PATCH 0
 PRERELEASE 149
-PRERELEASE_PATCH 1
+PRERELEASE_PATCH 2