* change the ci trt from version 5. to 6.0

* paddle-trt dynamic shape support init

* conv+bias or conv+bn dynamic shape support
test=develop

* modity trt engine opconvert
test=develop

* fix ci error
test=develop

* refine the profiler print test=develop

* support basic tensor.shape. 

* Support tensor.shape with dependencies. 

* polish detail implement of data loader, test=develop

* solve coverage ci problem, test=develop

In elementwise_min api doc has the error, all the api just use the elementwise_max op, we just correct the doc.

1. copy.deepcopy in NameVisitor should be changed to copy.copy to make hash or set work
2. read_context should be type of gast.Load()/gast.AugLoad(), not gast.Load/gast.AugLoad

fix concat_mkldnn op when encounter extreame conditions.

* reduce default attrs for dynamic graph, test=develop

* add some explanations for explicit attr, test=develop

* tweak explicit attr comments, test=develop

Add basic support for while in translating dygraph to static

1. Analysis the variable liveness in class NameVisitor
2. Replace while key word using while_loop API

* Added an option to use external FP32 model in QAT comparison test

test=develop

* Modify the way of inserting newly defined func_nodes test=develop

* fix loaded program load bug; test=develop

* first version

* speed backward engin; test=develop

* remove useless code; test=develop

* reconvery io.py; test=develop

* remove useless code; test=develop

* remove useless code; test=develop

* add recorded cuda memory apis, fix typo, test=develop

* add more ut, test=develop

* follow comments, test=develop

* fix py35 incompatible issues, test=develop

* encapsulate the PaddleTensorToLoDTensor, test=develop

* serialize the pd_tensor, test=develop

* serialize tensors to file, test=develop

* add fluid.device_guard to specify the device type for Op

* functional dygraph enable/disable
test=develop

* use context manager instead
test=develop

* refine sample code
test=develop

* rename api & expose to fluid
test=develop

* fix sample code
test=develop

* test=develop, optimize distributedstrategy

test=develop

* change the function in op_teller, test=develop

* correct the commit-id, test=develop

Fix the big shape op test, elementwise_mul, elementwise_div, mul op
Fix the precision op test, mul op

* polish the profiler doc

* update ScopeBufferedSSAGraphExecutor&AsyncSSAGraphExecutor&ThreadedSSAGraphExecutor&FastThreadedSSAGraphExecutor&ParallelSSAGraphExecutor&ParallelExecutor for fetching unmerged results.

* add the unit test for fetch_unmerged.

* update ut for multi-card and multi-cpu.

* add the error message and the user suggestion in FetchOpHandle. test=develop

* fix basic gru lstm parameter attr bug; test=develop

* fix bias attr bug; test=develop

* add basic lstm gru name unitest; test=develop

fix bug that sourcecode of third_party can't be cached correctly,and add cache for xbyak and openblas (#22772)