fix(ec2): exposed userDataCausesReplacement in BastionHostLinuxProps (#31416)

### Issue # (if applicable)

Closes #31348.

### Reason for this change
When creating a Bastion host, customer is using instance's userData to write approved public keys to `.ssh/authorized_keys`. However, when changing the list of authorized keys, it does not trigger the instance to be replaced, so the modification has no effect.

### Description of changes
Exposed `userDataCausesReplacement` in `BastionHostLinuxProps`. The value is passed down to downstream `AWS::EC2::Instance` resource.

### Description of how you validated changes
Added unit and integration tests.

**NOTE:** Re-invoking `Template.fromStack(stack)` doesn't change the resource Id, so unit test uses 2 stacks. May be invoking `Template.fromStack(stack)` caches the results and doesn't refresh it.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: ashishdhingra