fix: update devtool all command so that it works when run from a freshly-cloned repo

[danielezhu]

Issue #, if available:

Description of changes:
Currently, our Github actions job is doing the following:

./devtool env_setup
./devtool install_deps
./devtool unit_test_with_coverage
./devtool build_package

./devtool all currently does almost the same thing, except instead of step 2, it does install_poetry instead of install_deps.

As a result, if you run devtool all right after cloning this repo, the unit_test_with_coverage command will fail because import statements in unit tests will fail. The key command that needs to be run is poetry install, which gets called by install_deps. This will install not only the project dependencies, but the project itself, which is critical for import statements to work.

Note that subsequent calls to devtool all will not take a long time re-installing all of the dependencies; if there is no change to the dependencies, install_deps is basically a no-op.

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