feat: Remove previewnet, testnet, mainnet configuration

[natanasow]

Description:

Remove previewnet, testnet, mainnet configuration for several reasons:

1. They are unused from most, if not all users.
2. It's almost as easier to start with whatever container you want, just by specifying using --network-tag or --mirror-tag or --relay-tag
3. Because of them, we need to overide env. varibles, which create unnecessery complications when used in CI.

Related issue(s):

Fixes #589

Notes for reviewer:

Checklist

• [ ] Documented (Code comments, README, etc.)
• [ ] Tested (unit, integration, etc.)

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud