[flang][NFC] update some old tests to HLFIR lowering (#127230)

Update some LIT tests that are using the legacy lowering to use HLFIR.

This makes testing more modular and is a step towards getting rid of the
legacy lowering (that is only kept because of the tests).
There are many more.

I deleted a couple file that were very specific to the legacy lowering
(e.g. array-copy).

Author: jeanPerier