:four_leaf_clover: `Proposal`: Use DevStream in an Air-gapped Environment

What Would You Like to Add? Why Is This Needed?

See #1082 for more background info.

Design

• [x] Add a script for dtm and dtm plugins downloading @aFlyBird0
• [x] Add a script for helm charts downloading @aFlyBird0
• [ ] dtm plugins customize image repository supproting @daniel-hutao
• [x] dtm local charts installation supporting @daniel-hutao
• [ ] Jenkins: add a script for Jenkins plugins downloading @steinliber
• [ ] Add some documents for the dtm air-gapped using @daniel-hutao
• [ ] List all images needed by jenkins and harbor @daniel-hutao

Anything else

Go Go Go ^-^