Bug casting from uint pdarray to strings/float

[stress-tess]

We currently don't have the ability to cast from a uint pdarray to a strings. I found this while reviewing the pdarray_creation_tests PR

# int pdarray converts just fine
>>> ak.cast(ak.arange(10), str)
array(['0', '1', '2', '3', '4', '5', '6', '7', '8', '9'])

# uint pdarray causes errors
>>> ak.cast(ak.arange(10, dtype=ak.uint64), str)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[12], line 1
----> 1 ak.cast(ak.arange(10, dtype=ak.uint64), str)

RuntimeError: Error: castMsg: UInt64 : str not implemented

The issue seems to be this block. For all other types we do "str" not "string"

arkouda/src/CastMsg.chpl

Lines 85 to 87 in 5eb7b5f

	when (DType.UInt64, "string") {
	return new MsgTuple(castGenSymEntryToString(gse, st, uint), MsgType.NORMAL);
	}

Similarly we can't cast from uint to float because we write "float" instead "float64"