(deadline): Add UserData property to WorkerInstanceFleet

The current WorkerInstanceFleet construct does not allow providing a UserData object at creation for it to use. The feature request is to make it possible to do so.

### Use Case

Some UserData needs to be run on every start of the instance, or at least survive a reboot. e.g. When joining an instance to an AD and then to an FSxWindows drive you must join the AD, reboot the instance, and then join the FSx. Doing this in UserData requires persisting the UserData; persisting UserData can only be done on Linux by using a [Multipart UserData](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_ec2.MultipartUserData.html) rather than an ordinary UserData.

### Proposed Solution

Simple enough. PR incoming...

* [X] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

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This is a :rocket: Feature Request

Start by locating the WorkerInstanceFleet construct and reviewing how its creation options currently handle UserData. Compare the requested UserData object with AWS CDK's MultipartUserData behavior; done means callers can provide UserData when creating the fleet and the supplied data is used on instance starts, with relevant tests updated.

Written by the indexing model from the issue text.