Merge pull request !5300 from nhussain/slice_op

add string implementation, can handle partial string slices

finish core implementation, added Index object

fix up the logic

add in new SliceOption object, cleaning up tests

Leaf ops do self-reset.

embed python compose op

add implicit compose op

more tests

change ImagefolderDV2 name

change ds.transforms.vision to ds.vision

change batch api to match map api more closely

compose op changes

test_pylint

remove compose op from vision, move to transform module, refactor map and batch to use column_order

python part of random ops

added random select sub policy

validators added

comments added, remaining issues addressed

add more python test cases

fix ci

fix CI

fix order of include files

addr review cmts

addr review cmts

reorg file

fix compile err

address review cmts

address review cmts

fixed random_apply tests

fix validators

fixed random_apply tests

fix engine validation

remove graphengine changes

concat op

Truncate Pair

concat_op

remove graph engine changes

Signed-off-by: leonwanghui <leon.wanghui@huawei.com>