ClearlyDefined could not support Go component with more than 5 '/' in the module path

The route here, [router.get('/definitions/:type/:provider/:namespace/:name/:revision/:extra1?/:extra2?/:extra3?')](https://github.com/clearlydefined/service/blob/0d00f25fa21587693ef6a703db5b4e542eadfaf6/routes/definitions.js#L23), is added for Go component support. For example, the Go component, named `github.com/quasilyte/regex/syntax@v0.0.0-20200407221936-30656e2c4a95`, will translate to `Get /defintions/go/golang/github.com/quasilyte/regex/syntax/v0.0.0-20200407221936-30656e2c4a95`. And all the params are parsed like: `type=go, provider=golang, namespace=github.com,name=quasilyte, revision=syntax, extra1=v0.0.0-20200407221936-30656e2c4a95`. Then ClearlyDefined is trying to create a go coordinate based on this [logic](https://github.com/clearlydefined/service/blob/0d00f25fa21587693ef6a703db5b4e542eadfaf6/lib/utils.js#L65).

However, the`extra1, extra2, extra3` is not extensible because it will not work for the Go component with a module path that has more than 4 slashes, like `github.com/azure/go-autorest/autorest/azure/cli@v0.4.2`.

After some discussion with the community, there are two options.
Option1, use express regex route to replace `/definitions/:type/:provider/:namespace/:name/:revision/:extra1?/:extra2?/:extra3?` with `/:type/:provider/:namespace/:name/:revision/*`and we could get all extras from `req.params[0]`.
Pro:
1. Don't change the existing API.
2. Simple to fix.

Con:
1. It's still a hacky way.

Option2, add another route `/definitions?type=type&provider=provider&namespace=namespace&name=name&revision=revision`. All the parameters are moved from path params to query params because param params could support any characters by url encoding.
Pro:
1. Long-term solution and more extensible. In the future, it could support scenarios when the name or provider also contains slashes.

Con:
1. An extra API to get a definition may confuse the community.
2. Probably needs to do some API versioning which we may need to do some extra work.