Add Task Designer allowing to run individual tasks with custom inputs

[Ben8t]

Feature description

Create a space where users can test and play with tasks, flows, triggers without worrying about data, connections, etc..

Like "unit test" for Kestra Flows.

• A space where users have the possiblity to create "fake data"/"fake outputs" (or read from previous executions)
• In the editor adding the possibility to connect to the "playground" : "test this task in Kestra Playground
• Creating a Flow, validate tasks input/outputs, test them indidually then can test the whole flow

[anna-geller]

it might be worth considering adding an optional boolean property dryRun to each task or trigger (or perhaps even on a flow level) to allow running things as if they were using real data even when using fake passwords, connection details, etc -- only to test the flow of something

[anna-geller]

related #1953

[anna-geller]

closing all duplicates and keeping only the recent epic including the designs from onsite 🚀