feat: Add StackingControls for Managing zIndex

[camielvs]

Description

Adds manual zIndex management to ReactFlow nodes. This is accessible in the UI via the new StackingControls component.

This PR adds:

• Defaults & Ranges for allowable zIndices for each node type
• Utilities for managing stacking actions (move to front/back etc)
• A Component that consumes all of this and renders four interactive buttons for the user to control these features:
  • Move Forward
  • Move Backward
  • Bring to Front
  • Send to Back

This is an enabling PR for Flex Nodes, as manual zIndex management is a desired feature for Sticky Notes.

Motivation for a generalised solution:
Changing the default ReactFlow behaviour for zIndexMode from basic to manual results in nodes no longer being brought to front when selected. To mitigate this the PR brings the entire zIndex Management feature to all nodes so users can manually deal with the stacking themselves (rather than have no options at all). Upstack the feature will be added for Task and IO nodes.

Related Issue and Pull requests

Progresses https://github.com/Shopify/oasis-frontend/issues/483

Type of Change

• New feature

Checklist

• I have tested this does not break current pipelines / runs functionality
• I have tested the changes on staging

Screenshots (if applicable)

Test Instructions

Additional Comments

Note: this PR doesn't actually implement the new component anywhere int he UI - that comes upstack. Focus reviews on business logic and implementation.

[camielvs]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: Add StackingControls for Managing zIndex #1756 : 2 dependent PRs (#1728 , #1758 ) 👈 (View in Graphite)
• chore: Node Definition Cleanup #1731
• master

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