Support WHILE with growing output tensor in CpuExecutor

1. Adds a WHILE test that produces a tensor of dynamic size. The loop
   body model has inputs and outputs of unknown rank.
2. Adds an IF test where the branch models have unkown input and output
   ranks.
3. Modifies the partitioner to avoid trying to delegate referenced
   models if an IF or WHILE or their associated referenced models have
   unknown dimensions.
4. Adds dynamic loop output shape support to CpuExecutor by allocating
   new temporaries on each iteration.

Bug: 132458982
Bug: 154597673
Test: NNT_static --gtest_filter='*_dynamic*'
Change-Id: I8da1aa92abf090adbdcbf647c113fe27f4c002d8
7 files changed
tree: d4553ec8d46caf3cc24126009e1b69609bae843b
  1. nn/
  2. .clang-format
  3. CleanSpec.mk
  4. CPPLINT.cfg
  5. OWNERS
  6. PREUPLOAD.cfg