Ability to get actually full path/URL, e.g. from ObjectMeta

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**

It would be nice to have a function/attribute to give me the full URL for an object. Currently, the ObjectMeta.location provides the path _within_ the object store but I would like to get the full URL such as "gs://bucket/dir/file.txt".

**Describe the solution you'd like**

Maybe add an attribute "uri" to the ObjectMeta struct or provide a new function `.get_uri` on the ObjectStore struct.

**Additional context**

The reason I am looking for this is that I need to pass the URL a different program and it would be nice to keep all the logic centralised in the object_store library instead of having a separate function with "if gcp: "gs://" + path elif aws: "s3://" + path" etc.

Start by locating the ObjectMeta and ObjectStore definitions and reading how location and provider configuration are represented. Compare the requested ObjectMeta uri attribute with an ObjectStore get_uri method, then check existing tests for object-store URLs. Done means a consistent provider-specific full URI can be obtained without callers rebuilding it themselves.

Written by the indexing model from the issue text.