Move version out of SDK. For now it's a copy rather than move: the part not addressed by this change is sdk/helper/useragent.String, which we'll want to remove in favour of PluginString. That will have to wait until we've removed uses of useragent.String from all builtins.
* Removes _builtin_ versions from mount storage where it already exists
* Stops new builtin versions being put into storage on mount creation/tuning
* Stops the plugin catalog from returning a builtin plugin that has been overridden, so it more accurately reflects the plugins that are available to actually run
Add plugin version to GRPC interface
Added a version interface in the sdk/logical so that it can be shared between all plugin types, and then wired it up to RunningVersion in the mounts, auth list, and database systems.
I've tested that this works with auth, database, and secrets plugin types, with the following logic to populate RunningVersion:
If a plugin has a PluginVersion() method implemented, then that is used
If not, and the plugin is built into the Vault binary, then the go.mod version is used
Otherwise, the it will be the empty string.
My apologies for the length of this PR.
* Placeholder backend should be external
We use a placeholder backend (previously a framework.Backend) before a
GRPC plugin is lazy-loaded. This makes us later think the plugin is a
builtin plugin.
So we added a `placeholderBackend` type that overrides the
`IsExternal()` method so that later we know that the plugin is external,
and don't give it a default builtin version.
