FEATURE: Add node migration transformation to change properties from scalar to BackedEnum

[nezaniel]

this is a followup feature for neos/flow-development-collection#3523 (comment)

Since now we have fully fledged enum support for node properties, this now adds a node transformation that retroactively changes previously set strings (or ints) to their \BackedEnum counterparts - given the NodeType configuration has been adjusted beforehand.

Upgrade instructions

none

Review instructions

see tests

Checklist

• Code follows the PSR-12 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the 9.1 branch as this is a new feature
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[nezaniel]

Now that I think about it, the target type can be fetched from the node type instead of being declared manually.
/adjusted