Using a callback to set a resolve_url is not particularly idiomatic.
Deprecate it in favor of the `set_instance_url` and
`set_instance_pushurl` functions which can now be called from the
`git_remote_ready_cb` callback.

Introduce a new callback that fires when the remote is ready to connect.

Users may want to override the URL on a particular instance of a remote,
instead of updating the configuration.  Previously, users could use a
callback to do this, but this is not particularly idiomatic.

We _dispose_ the contents of objects; we _free_ objects (and their
contents).  Update `git_strarray_free` to be `git_strarray_dispose`.
`git_strarray_free` remains as a deprecated proxy function.

The code worked under the assumption that anything under `refs/tags` are
tag objects, and all the rest would be peelable to a commit. As it is
completely valid to have tags to blobs under a non `refs/tags` ref, this
would cause failures when trying to peel a tag to a commit.

Fix the broken filtering by switching to `git_revwalk_push_glob`, which
already handles this case.

Since libssh2 doesn't read host configuration from the config file,
this callback can be used to hand over URL resolving to the client
without touching the SSH implementation itself.

Move to the `git_error` name in the internal API for error-related
functions.