Add int64 Tperm type support for `Transpose` (#13909)

* Add int64 Tperm type support for `Transpose`

This fix adds int64 Tperm support for `Transpose`. In
`array_ops.cc`, `Transpose` and `ConjugateTranspose`
have been specified as accepting int32 and int64 perm
types. However, only int32 kernels has been registered.

This fix adds the int64 perm support by removing
the constraint on Tperm, resolve the type at runtime,
and copying the data type accordingly to correctly handle
the int64/int32 types.

Additional tests have been added as well.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add test cases for int64 of perm in Transpose.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Add namespace to hide PermutationHelper

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Enable use_gpu=True for perm type test.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* extra // namespace annotation

* Adding a comment about int32 casting that should be safe.

Permutations only contain values that refer to dimensions, and the maximum number of dimensions we have is 254, so an int32 is always safe here.