Procedures: Mark unstable for initial release

[gefjon]

In the module bindings libraries, feature-flag the procedure methods behind our unstable feature for the initial release.

[gefjon]

Also move the /v1/database/:name/procedure/:func route under the unstable path component, unless #3659 is already done.

[aasoni]

@gefjon just wanted to bring up that we have a proposal for reworking the database naming system. This would allow slashes in database names.

This is relevant for this ticket because of this section in the proposal.

the tl;dr is that for database slashes to work, existing APIs under database/:name_or_identity will require url encoded slashes which is not great user experience. A new set of APIs are proposed to mirror functionality but moving the :name_or_identity url parameter to the end to avoid ambiguous routing. E.g. database/:name_or_identity/reducer/:name -> database/reducer/:name_or_identity/:name

If the proposal is approved (happy for your input as well) new api end points under database/ should follow the new scheme so that they can support database with / in the name.

[gefjon]

@aasoni some time after moving it under unstable, we intend to remove the separate procedure route in favor of making /v1/database/:name/call/:func able to transparently invoke both reducers and procedures.