[devel_transport] Add greentea-client dependency detection

[PrzemekWirkus]

Change:

• In order to detect if yotta module is using greentea-client (and new Greentea 0.2.x with async host test model) we need to add API for Greentea before and after devel_transport changes.
• Greentea before v0.2.x (mbed-greentea<0.2.0) should:
  • detect presence of greentea-client dependency/testDependency (in module.json) and if such exist propose upgrade to latest greentea: pip install mbed-greentea>=0.2.0 --upgrade.
  • if no greentea-client dependency/testDependency in yotta module - normal operation.
• Greentea from v0.2.0 (mbed-greentea>=0.2.0) should:
  • detect presence of greentea-client dependency/testDependency (in module.json) - normal operation.
  • if no greentea-client dependency/testDependency in yotta module (in module.json):
    • Propose downgrade to Greentea before v0.2.0: pip install mbed-greentea<0.2.0 --upgrade or
    • propose solution (point to porting guide for new async model).