[MV3 Beta Bugs] Invalid "Target" in Redirect Rules UI

[lidel]

This is not blocking #1182, just something to improve in follow-up PR.

The way rules for subdomain gateways are presented make no sense, looks like a bug:

To reproduce above rules, try opening:

1. https://dweb.link/ipns/ipfs.tech
2. https://blog.ipfs.tech/
3. https://docs-ipfs-tech.ipns.dweb.link/ → the Target here is due to a separate bug described in [MV3 Beta Bugs] Single catch-all rule per subdomain gateway #1278

Suggestions:

• remove <resource-path>: it is not used correctly, never indicates actual content path
• keep things simple, use the original identifier of the capture group in regex (\1, \2, or \3), this way you don't need to have different label for one of 3 cases, and its the same as the actual rule