chore: Add FlexNode Update Hook

[camielvs]

Description

Collated all instances of flex node spec updates into a hook so simplify DRY code.

Related Issue and Pull requests

Type of Change

• Cleanup/Refactor

Checklist

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

Screenshots (if applicable)

Test Instructions

• Confirm sticky notes still work as expected

Additional Comments

[camielvs]

Warning

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• feat: Edit FlexNode Titles via Double-Click #1837
• chore: Add FlexNode Update Hook #1836 👈 (View in Graphite)
• feat: Variable Font Size for Flex Nodes #1832
• feat: Lock Flex Nodes #1826
• feat: Transparent Flex Nodes can have a Border #1784
• feat: Double-Click to Edit Flex Nodes in-place #1783
• feat: (Un)Pack Flex Nodes into Subgraphs #1769
• feat: Duplicate Flex Nodes #1768
• feat: zIndex Management for Flex Nodes #1755
• feat: Resizable Flex Nodes #1743 : 1 other dependent PR (#1744 )
• feat: Add Color Picker #1738
• feat: Edit Sticky Note Content #1737
• feat: Context Panel for Flex Nodes #1735 : 1 other dependent PR (#1736 )
• feat: Delete Flex Nodes #1746 : 1 other dependent PR (#1747 )
• feat: Add Sticky Notes to Canvas #1729 : 1 other dependent PR (#1745 )
• feat: Add Basic FlexNode #1728
• feat: Add StackingControls for Managing zIndex #1756 : 1 other dependent PR (#1758 )
• chore: Node Definition Cleanup #1731
• master

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