`graph init`: revisit parameters and flow

[YaroShkvorets]

There is quite a bit of technical debt with parameter validation. Multiple checks for required/incompatible flags result in spaghetti code and bugs.

Confusing flag combinations result in bad DX, there are a few that no longer needed and can be removed.

Need to streamline and simplify validation and re-evaluate some flags prior to v1 release.

There are 4 ways to init subgraph from command line in non-interactive way:

• --from-contract
• --from-example
• --from-subgraph
• --spkg

1. If one of the --from-* flags is specified then all required flags need to accompany it or command should fail.
2. If --from-* is not specified we follow interactive flow.
3. Why --spkg? Change to --from-substreams for uniformity
4. Each --from-* should have its own method with required/incompatible flag checks
5. Leverage oclif flag validation where possible
6. Remove --skip-git flag as planned
7. Remove --protocol flag, since we have that information in the registry.