feat: support adding advanced task definitions to environments

[jackwrfuller]

Description

• Requires feat!: support addition of advanced task definitions to environments machinery#127
• Resolves Add a "lagoon add task ..." command #233
• Could continue work to additionally resolve Add arguments to invoke task #262

This PR introduces support for adding COMMAND-type advanced task definitions to lagoon environments via the command

lagoon add task-definition -p project -e main [-f filepath | -S service -c command -d description -C confirmation]

Simple definitions (i.e those with only a command, description, and confirmation text) can be done directly via cli arguments. Otherwise, if the user specifies a file path via the -f option, then the cli will read in a task definition defined in a YAML file. The file method is more full-featured, and supports most of the advanced task definition functionality available. For example:

name: "example task"
description: "example task"
confirmationText: "Are you sure?"
service: cli
command: "echo $MY_VAR"
permission: DEVELOPER
deployTokenInjection: true
projectKeyInjection: true
adminOnlyView: false
arguments:
  - name: MY_VAR
    displayName: "My Variable"
    type: NUMERIC
    optional: false
    defaultValue: "1122"

Limitations

• Doesn't yet support the IMAGE task definition type
• At this point in time, only supports defining a task definition on an environment (not project)