stream-clone: add a explicit set list requirements relevant to stream clone This set explicitly lists all the requirements that "stream clone" will preserve. Any other one will not be preserved. The role of listing the relevant one was previously filled by `repo.supportedformat`, but it seems clearer to use that such global and explicit set. The `repo.supportedformat` attribute will be cleaned up in a later changeset The true meaning of `repo.supportedformat` vs `repo._basesupported` was lost over time so, the content is currently bad. For example, `dirstate-v2` is currently considered relevant to the stream clone, or internal phase is missing. We kept the same content in this changeset and we will fix them later. Differential Revision: https://phab.mercurial-scm.org/D12032