Switch pipeline and workflow undo/redo to XML snapshots, fixes #8037

[mattcasters]

What

Replace incremental ChangeAction replay for pipelines and workflows with gzip-compressed XML snapshots of the whole document.

Undo/redo no longer reconstructs graphs from typed deltas (new/delete/change/position + nextAlso chaining). It restores the previous or next snapshot into the existing PipelineMeta / WorkflowMeta object.

This is the same approach that made undo/redo reliable in hop-data-vault modelers.

Why

The old system was error-prone:

• Replay depends on indexes, clones, hop endpoint names, and nextAlso.
• Combined transform+note moves could desync because addUndoPosition dropped nextAlso.
• Workflow redo of an action edit hit ChangeTransform instead of ChangeAction.
• Transform dialogs only recorded undo when a clone/XML compare said so, so missed edits were neither undone nor marked dirty.

PipelineMeta.clone() already tells callers to serialize to XML. Snapshots use that path (XmlMetadataUtil, no license header / formatter).

How

• New XmlSnapshotUndo stores gzip XML stacks, trimmed to PropsUi.getMaxUndo() (default 100).
• Pipeline and workflow graphs own the stacks and restore into the live meta without firing file-load extension points.
• Dialogs, paste, drag, snap/align, and notes snapshot before the mutation (one undo step for compound actions).
• Leftover hopGui.undoDelegate.addUndo* calls still work through a post-change shim (plugins included).
• After undo/redo, the dirty asterisk follows whether the current snapshot matches the last saved one.
• TableView cell undo is unchanged.

GUI

Configuration perspective → Explorer Perspective: Maximum undo operations (PropsUi.getMaxUndo()). CLI: --max-undo.

Tests

XmlSnapshotUndoTest covers pipeline/workflow round-trip, redo clearing, max-undo trim, apply-without-recording, and gzip content equality.

Issue

Fixes #8037