add support for MindRecord and TFRecord
----
optimize tensorshape

optimize tensorshape and FlatIndex

TFRecord and MindRecord support for string tensor

Modify mem layout
Add new constructor
Add method Allocate

Change some GetMutableBuffer usages to AllocateBuffer

implementation 99% complete

everything and tested except for repeatable shuffling

tested most basic/typical split usecases

cleanup

some more cleanup

fix CI

more ci fix

more ci fixes

more ci fix

more ci fix

more ci fix

added more tests, fixed some bugs

some more clean up and test cases

added shard/shuffle before split warning/error

addressed code review comments and ci

fixed ci

-replace switch'case by indexing

- Add test case
- Add constructors
- Add getItem string

- Fix bugs
- Add more tests

- Tensor iterator
- asNumpy
- TextFileDataset

- Tensor(Numpy)

- Super > 2D
- Add more test cases for GeneratorDataset

- Change StartAddr to GetBuffer and GetMutableNuffer

- Raise an error if batch is used with strings

Clean-up work

clang format updates

self-review cleanups

cpplint fix

review updates

ci fixes

fix ut

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