Dy2stat didn't support tuple as iteration variable in the past. This PR added there main cases:

       1). Non-enumerate case: for var1, var2 in var|var.numpy() will be re-written as:
          for FOR_ITER_TUPLE_PREFIX_x in var | var.numpy():
            var1 = FOR_ITER_TUPLE_PREFIX_x[0]
            var2 = FOR_ITER_TUPLE_PREFIX_x[1]
        2). Enumerate out tuple case: for t in enumerate(var|var.numpy) will be rewritten as:
          for FOR_ITER_TUPLE_INDEX_PREFIX_x, FOR_ITER_TUPLE_PREFIX_x in enumerate(var|var.numpy):
            t = (FOR_ITER_TUPLE_INDEX_PREFIX_x, FOR_ITER_TUPLE_PREFIX_x)
        3). Enumerate inner tuple case: for i, (var1, (var2, va3)) in enumerate(var|var.numpy()) will
        be re-written as:
          for i, FOR_ITER_TUPLE_PREFIX_x in var | var.numpy():
            var1 = FOR_ITER_TUPLE_PREFIX_x[0]
            var2 = FOR_ITER_TUPLE_PREFIX_x[1][0]
            var3 = FOR_ITER_TUPLE_PREFIX_x[1][1]

* fix a bug of Sequential::__getitem__, test=develop

* add testcase, test=develop

* polish printing dtype

* fix special case

* delete empty line of pybing.cc, test=develop

* fix layers train eval bug, test=develop

* add paddle.

* add unittest

Set expected place in child thread for dataloader to avoid costing cuda memory on other card (#30338)

* set expected place in child thread for dataloader

* set device id when set tensor from numpy

* revert tensor_py change

* add compile guard

* fix ci

* fix bug

* Fix bug for 'save mutiple method'

* To pass coverage.

* edit code to pass coverage.

* edit code to pass coverage.

* add unittest for coverage.

* change for coverage.

* edit for coverage.

Add clone method for static Variable so that this interface will be same as dygraph. It fixed some bugs in dy2stat

* delete paddle.nn.functional.assign

* fix dynamic to static error

* fix tensor shape bug

* fix op_num

* clean code

1. When x is Variable, call nn.shape(x) only in following cases:
 1）The shape of x is used in control flow condition.
 2）The dim to be used is negetive
2. When x is Variable, but x.shape or x.shape[idx] doesn't contain negetive value, don't convert to paddle.shape()

* Polish and Optimize the print/repr message of all layer

* fix some code format

* add distributed.split, test=develop

fix the state_dict bug for the xpu

* fix fleet for multi-stream

* fix memcpy for ncclid

* use sync to solve move operation

[Dy2Stat] Fix bug for loop: a variable is used and created in loop, but used before created (#29769)

Enable jit.save to Save Without Running.

Support to transformfor ele in var stms in which var is a slice of Tensor.

[Dy2Stat] 1. Fix bug of for-range stmts. 2. Support that step value is negative in for-range stmts (#29519)

1. Fix error in _build_cond_stmt of for-range stmts. 

2. Support that step value is negative in for-range stmts

3. Fix code because of the diff between Py2 and Py3

* add fast path for p == 0 in dropout

* add ut

* Add ReserveSpace in dygraph batch_norm.

* Add unittest for reservespace

* support deepcopy for Layer/Tensor/Paramerbase

* fix some code

* add tensor_indices in AssignGroupBySize

* add rebuild group in reducer

* fix the bug of reducer in embedding

* add comment

* rm complexvariable

* modify test_var_base unittest

* remove duplicated codes

Reduce exception type so that if covert_to_static failed, it reports right error message.

[Dy2Stat] Fix bug: Do not use gast.Subscript to replace gast.Name in when transforming for_enumerate_loop (#29310)

* basic impl of type promote

* add comment & another testcase

* fix complex bugs & support python op promote type

* fix failed unittests & polish code

* add unittest for coverage

* change to only promote complex type

* polish code details

* polish several comments