Add SignalFillEmptyd tranform

[matt3o]

As mentioned here #2637 (comment) , this transform helps to fix NaN values after the input transforms.
It is basically only a wrapper around SignalFillEmpty.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[wyli]

looks good to me, please add a unit test following the existing one https://github.com/Project-MONAI/MONAI/blob/dev/tests/test_signal_fillempty.py

not sure if replacement should allow for different inputs for different items in the keys, I guess we can expand the logic later if needed.

[matt3o]

@wyli Sweet, thanks! I'll go add the tests and add it to the symbol table.

Also I realized the array test is broken: https://github.com/Project-MONAI/MONAI/blob/dev/tests/test_signal_fillempty.py#L27C1-L36C1

self.assertTrue(not np.isnan(fillemptysignal.any())) always evaluates to True if there is any non-zero value in the array. Can I fix that in this commit as well or do you want a separate one?
The fix is simple self.assertTrue(not np.isnan(fillemptysignal).any())

[wyli]

thanks @matt3o please include the test case fix in this PR..

[wyli]

/build