Renaming model approval as training plan approval

This merge request is for changing model approval variables, names/strings to training plan approval.

Changes has been applied to:

• node/model_manager -> node/training_plan_security_manager.py
• node/node.py
• node/round.py
• node/cli.py
• fedbiomed_run script
• common/environ.py
• researcher/job.py
• related unit tests
• related GUI Flask/React components
• related file/folder names

Guidelines for MR review

General:

• give a glance to DoD
• check coding rules and coding style
• check docstrings (eg run tests/docstrings/check_docstrings)

Specific to some cases:

• update all conda envs consistently (development and vpn, Linux and MacOS)
• if modified researcher (eg new attributes in classes) check if breakpoint needs update (breakpoint/load_breakpoint in Experiment(), save_state/load_state in aggregators, strategies, secagg, etc.)