Introduce deterministic resolver for alternative sources for dependencies in forc-pkg

[kayagokalp]

Currently syntactically we can insert alternative sources for each dependency in the Forc.toml file.

std = { ipfs = "bafybeighr56cwvhje2hxc5gtdiqgxia4slmcbcjvjdflqkmjxukvatqley", git = "https://github.com/fuellabs/sway" }

But forc-pkg's behaviour is undefined at the moment. We should be resolving these alternatives sources in specific order for ensuring correct behaviour for building.

For example if a source has a path source, git source and a registry source, we should not be using the registry version. Because there might be local changes. The registry version is there to enable to be published to the registry.

To reduce further ambiguity cargo does include the following sentence to their docs:

It is possible to specify both a registry version and a git or path location

It is clear that a user can specify a registry version and git or registry version and path. This way the disambiguity between the precedence of path and git is removed.

The summary of this propsed change is that:

1. Disallow git, path, ipfs to be declared at the same time
2. But they can be matched with registry version