This reverts commit 1ca28598, reversing
changes made to b703c9f9.

Revert created with the following command:
```
git revert 1ca28598 -m 2
```

And restore -layering_check to a few places where it got removed with https://github.com/tensorflow/tflite-micro/pull/435/

BUG=http://b/177257332

Moving forward, TFLM support for Arduino is going to be maintained in a
stand-alone repository at:
https://github.com/tensorflow/tflite-micro-arduino-examples

BUG=http://b/193823889

* Add files from TfLite

Added batch_matmul.h and tensor_utils_common.h that are needed for the BATCH_MATMUL operator.

* Arduino library creation for CI build.
Issue# 256

* fix bug with include file path flattening

* fix examples path generation

Some files in examples source and headers list are not in the examples directory.  They can be tensorflow files or third-party files.  The code is corrected so that these files end up inside the generated directory tree.  Previously, these files were being placed outside the generated directory tree and were thus invisible to follow-on targeted generation scripts.

* remove/revert files that go into the arduino-examples repo

* Format with:

```
tensorflow/lite/micro/tools/ci_build/test_code_style.sh --fix_formatting
```

* request changes to PR

* Removed symbolic link for micro_speech example from Makefile.
Added additional include flags to Makefile.
Adjusted header file transformations during base tree creation.
Co-authored-by: NAdvait Jain <advaitjain@users.noreply.github.com>
Co-authored-by: NAdvait Jain <advaitjain@google.com>

* Groundwork to enable python format checks (via yapf) as part of the CI.

With this change:
 * we are set up to use yapf as part of the docker container
 * pigweed patch is updated to use the google Python style (pep8 with indent of 2 spaces)
 * some documentation updates.

The code still needs to be formatted, and then the Python formatting check will be turned on as part of ci.

BUG=http://b/194404216

* Format all the code.

Once this change is merged, we will turn on Python formatting check as
part of the CI.

* minor formatting update.

BUG=http://b/193437031

* Separate core, kernel and third party objects.

Add a second optimization level in the Makefile to enable different
levels between kernels and the rest of the TFLM code. This results in a
smaller binary with minimal performance impact compared with using a
single optimization level.

Allows the use of implicit patterns to compile all sources, choosing
different flags for core, kernel and third party sources.

The following measurements are taken using the hexagon toolchain +
hexagon-size and hexagon-sim.

For the keyword benchmark using -O2:
   text    data     bss     dec
  58140   37639   46612  142391

  Cycles: 1700364

For the keyword benchmark using -O2 for kernels and -Oz for framework:
   text    data     bss     dec
  52796   37623   46612  137031

  Cycles: 1759664

* Make the optimization level log an error.

Remove OPTIMIZATION_LEVEL setting for bluepill since core framework now automatically is compiled with -Os.

* Remove section that builds bluepill with -Os since default uses -Os.

* Disable -Werror=vla in order to pass stm32 bare lib presubmit.

* Chnage order so that -Wno-vla takes priority over -Wvla
Co-authored-by: NAdvait Jain <advaitjain@users.noreply.github.com>

* Revert "Disable currently failing test to make the Xtensa build green. (#124)"

This reverts commit 20cdd3fb.

* Cherry pick https://github.com/tensorflow/tensorflow/pull/50072

* clang-formatting fix.

* Disable currently failing test to make the Xtensa build green.

BUG=https://github.com/tensorflow/tflite-micro/issues/123

* excluded some additional tests that were failing for Hifi5 and Vision P6.

* formatting fixes.

These are part of an already merged PR. We do not have proper checks for
the formatting as part of the github actions and hence these were only
caught by my local git hooks.

Bug: http://b/184876027