MNG-5578 cleanup redundant session binding in mojo executin scope

Signed-off-by: Igor Fedorenko <ifedorenko@apache.org>
MNG-5591 use 'reactor' hint for reactor WorkspaceReader

When maven is invoked from m2e, container.lookup(WorkspaceReader.class)
returns component with role-hint=ide, which I believe is a bug in Susi
or Guice (or at least well misunderstood feature). This masks
ReactorReader workspace reader implementation and breaks reactor
dependency resolution.

The solution is to use explicit "reactor" role hint for ReactorReader.
This avoids fuzzy default component lookup logic and guarantees reactor
reader is always used regardless of presence of other workspace readers.

Signed-off-by: Igor Fedorenko <ifedorenko@apache.org>