Add supported / unsupported version for fork enum

[terencechain]

This PR introduces unsupported versions (currently only Gloas), and tightened version.All() to hide those entries, and added version.IsUnsupported(). Tests were updated to enumerate and assert they never show up in All() or any testnet schedule.

[Inspector-Butters]

• I don't think Released() is a good name. since for example Fulu isn't released but is being returned by the function.
• it would be great to see an example of a test that uses the feature gated forks as well. (Released() + FeatureGated())

[prestonvanloon]

I'd rather see the language of "Unsupported" where a list of forks that are not fully supported are removed from version.All(). The purpose of having version.All() is to ensure that various areas of the code have support for all forks in the select statements in which all forks must be covered to support all forks.

[kasey]

You can get rid of the list and declare the keys directly in the map:

var unsupportedVersions = map[int]struct{}{
    Gloas: struct{}{}
}

Deletes this whole chunk of init code:

unsupportedVersionSet = make(map[int]struct{}, len(unsupportedVersions))
	for _, v := range unsupportedVersions {
		unsupportedVersionSet[v] = struct{}{}
	}
	sort.Ints(unsupportedVersions)

I think you can also drop the Unsupported func.