Proposal: avoid confusion over Flux scripts and files and `scriptID` (invokable) scripts and files

[jstirnaman]

Proposal in the making.

Decide on terminology for Flux script/file

• CLI docs use "Flux script file" to mean a file that contains "raw" Flux and is used to set the flux property for the task. The option terminology gets confusing with the advent of (invokable) script files that are referenced by tasks.
• See the Cloud API spec for tasks.
• See Cloud tasks can run invokable scripts and pass parameters. #4229

Relevant URLs

• Provide relevant URLs