This reverts commit b50eb97.

Reverts: #147171
Initiated by: QuncCccccc
Reason for reverting: tree is red due to a test in this PR
Original PR Author: Piinks

Reviewed By: {QuncCccccc, TahaTesser, bleroux}

This change reverts the following previous change:
**FYI for Reviewers:** Much of the API surface matches that of the 2D TreeView in flutter/packages#6592. If it changes here, it should change there, and vice versa.

📜  [Design Document](https://docs.google.com/document/d/1-aFI7VjkF9yMkWpP94J8T_JREDS-M3bOak26PVehUYg/edit?usp=sharing)

This adds classes and associated callbacks and controllers for TreeSliver. Core components:
- TreeSliver
- RenderTreeSliver
- TreeSliverNode
- TreeSliverController
- TreeSliverStateMixin
- TreeSliverIndentationType

Fixes #114299

https://github.com/flutter/flutter/assets/16964204/3facd095-7262-4068-aa33-d713e2deca99

https://github.com/flutter/flutter/assets/16964204/f851ae30-8e71-45c7-82a4-9606986a5872

flutter/flutter@c246ecd...27e0656

2024-06-05 98614782+auto-submit[bot]@users.noreply.github.com Reverts "TreeSliver & associated classes (#147171)" (flutter/flutter#149754)
2024-06-05 [email protected] Feature: Add AnimatedList with separators (flutter/flutter#144899)
2024-06-05 [email protected] make output of flutter run web tests verbose (flutter/flutter#149694)
2024-06-05 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Request focus if `SemanticsAction.focus` is sent to a focusable widget (#142942)" (flutter/flutter#149741)
2024-06-05 [email protected] Roll Flutter Engine from e88469090fed to 11a32d43e3f6 (2 revisions) (flutter/flutter#149699)
2024-06-05 [email protected] Request focus if `SemanticsAction.focus` is sent to a focusable widget (flutter/flutter#142942)
2024-06-04 [email protected] Roll Flutter Engine from 3dd40156afb6 to e88469090fed (2 revisions) (flutter/flutter#149695)
2024-06-04 [email protected] TreeSliver & associated classes (flutter/flutter#147171)
2024-06-04 [email protected] Roll Flutter Engine from fe00f023666c to 3dd40156afb6 (3 revisions) (flutter/flutter#149692)
2024-06-04 49699333+dependabot[bot]@users.noreply.github.com Bump github/codeql-action from 3.25.7 to 3.25.8 (flutter/flutter#149691)
2024-06-04 [email protected] Prepares semantics_update_test for upcoming heading level changes (flutter/flutter#149671)
2024-06-04 [email protected] Identify and re-throw our dependency checking errors in `flutter.groovy` (flutter/flutter#149609)
2024-06-04 [email protected] Scrollbar thumb drag gestures now produce one start and one end scroll notification (flutter/flutter#146654)
2024-06-04 [email protected] Disable sandboxing for macOS apps and tests in CI (flutter/flutter#149618)
2024-06-04 [email protected] Roll Flutter Engine from e211c43f3dc1 to fe00f023666c (3 revisions) (flutter/flutter#149680)
2024-06-04 [email protected] Allow `find.byTooltip` to use a RegEx (flutter/flutter#149348)
2024-06-04 [email protected] Roll Flutter Engine from a6aa5d826649 to e211c43f3dc1 (8 revisions) (flutter/flutter#149658)

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Reland of #147171

It was reverted for a failing unit test that had passed in presubmit. Hopefully this sticks better.
Also fixed leaks in 37b10ad