Move DataSync validation after template rendering

[fat-catTW]

Move DataSyncOperator input validation out of __init__ so templated fields are validated after rendering during execution.

This also removes DataSyncOperator from the operator constructor validation exemptions list.

related: #70296

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[Avcu]

Hi @fat-catTW, I created a PR for this earlier and commented in the parent issue:

• PR: Move template-field validation out of init for Amazon DataSync operator #70324
• Comment: Move template-field validation/transformation out of operator __init__ (exemption-list burn-down) #70296 (comment)

[shahar1]

Already merged Avcu's solution :)
Feel free to implement for another operator.

[fat-catTW]

Got it.
Thanks for reviewing. :D