perf: ensure deepCopy in beforeValidate hook does not run unnecessarily for rest and graphQL API (#10666)

Previously, the beforeValidate hook was deepCopying input data. This
indirectly ensured that the passed input data was not mutated.

E.g., if you run the `payload.create` local API, you do not want that to
mutate the `data` object that is passed as an argument. This will create
issues if you attempt to use it multiple times.


This PR moves the deepCopy logic from the beforeValidate hook to the
start of the local API operation. This ensures that
- Input data is intentionally copied at the beginning which makes more
sense. Comment was added to explain why
- GraphQL and Rest operations are now faster, as we don't need to ensure
that the input data is not mutated for those => deepCopy only runs for
local API