Collections: better support for executing workflows

[josephjclark]

When running a workflow through the CLI which uses Collections, we ought to improve the support

• Detect whether any steps use collections.*
• For those steps, automatically add the collections adaptor to the execution plan
• Automate the generation of the top-level credentials object
• accept --lightning as an argument to use as the collections endpoint, defaulting to OPENFN_ENDPOINT
• accept --pat argument, defaulting to OPENFN_PAT

The worker does exactly these things. The CLI should too!

The collections command already adds support and precedence for the env vars and lightning argument. We should totally re-use this stuff for execute.