Revert "Fix ToolTask hang when grandchild processes inherit pipe handles (#13351)"

[JanProvaznik]

Reverts #13351 on the vs18.8 branch.

This reverts commit 6c499a7 (Fix ToolTask hang when grandchild processes inherit pipe handles).

[Copilot]

Pull request overview

This PR reverts the previously introduced ToolTask change (commit 6c499a72...) on the vs18.8 branch, restoring prior process-wait and stream-handling behavior and removing the associated ChangeWave entry and regression tests.

Changes:

• Reverted ToolTask’s Wave18_6-gated stdout/stderr EOF signaling and the custom “wait without EOF hang” exit logic back to legacy Process.WaitForExit() behavior.
• Removed two unit tests that covered the reverted ToolTask behavior (grandchild-inherited-pipe hang + output capture expectations).
• Updated ChangeWaves documentation by removing the reverted feature from the Wave 18.6 list.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/Utilities/ToolTask.cs	Reverts the Wave18_6-gated ToolTask process/pipe EOF handling back to legacy waiting behavior.
src/Utilities.UnitTests/ToolTask_Tests.cs	Removes the regression tests that validated the reverted hang fix and output-capture behavior.
documentation/wiki/ChangeWaves.md	Removes the reverted ToolTask hang fix entry from the Wave 18.6 feature list.

Comments suppressed due to low confidence (1)

src/Utilities.UnitTests/ToolTask_Tests.cs:1118

• This revert removes the two regression tests that covered (1) the historical ToolTask hang when a grandchild inherits stdout/stderr handles (#2981) and (2) output loss when using WaitForExit(int) (#10378). If this revert is intended to be temporary, consider keeping these tests (e.g., skipped with a clear reason tied to the revert) so the scenarios stay documented and can be re-enabled when the underlying issue is addressed.

            }
        }

        /// <summary>
        /// A simple implementation of <see cref="ToolTask"/> to sleep for a while.
        /// </summary>
        /// <remarks>

[JanProvaznik]

merge on monday to get to the next QB window