[SMRT] relax version requirements for interfaces and libraries

[beeb]

Description
The interfaces and libraries for data-streams use a pinned version (at the moment 0.8.19) which make them unusable in most projects that want to import them as dependencies. This is because it forces dependents to use the same version, which is often not possible.

Basic Information
The interfaces and libraries which have a too restrictive version pragma are here:

https://github.com/smartcontractkit/chainlink/tree/develop/contracts/src/v0.8/llo-feeds

A suggestion would be to use ^0.8.0 or even >=0.8.0 for interfaces.

Steps to Reproduce
N/A

Additional Information
N/A