[frontend][keras] Add support for TimeDistributed (apache#7006)

* First pass on modifying Keras importer to handle TimeDistributed

* Use squeeze inside TimeDistributed, add tests

* linter fixes

* More linting

* Even more linting

* Fix unused argument annotations

* Forgot one pylint annotation

* Forgot to set up data layout in _convert_activation

* Decouple data_layout from etab

* Linting fix

* Forgot to set data_layout argument

* Missed an etab.data_format, also test_conv1d was not in the test file's main

* Rebase fixes

* Linting fix

* _convert_lambda needs a data layout argument too

* linting fix too

* Lint the test file too

* Redundant variables

* Simplify further

* Another simplification

Co-authored-by: Steven Lyubomirsky <slyubomirsky@octoml.ai>

Author: slyubomirsky