Extend trust chain visualisation to show Policy evolution (versions) over time

### Problem description
Latest developments for #2236 to support policy chains introduced an expanded view of Guardian artefacts produced by policies, culminating in the issuance of tokens. This now covers almost all aspects of Guardian policy execution, with the notable exception of the provenance of the policy itself - its evolution from version to version. If this is added Guardian UI would become a powerful browser of the policy execution history useful for and beyond the original trustchain concept.

### Requirements
Add the capability to navigate to the screen/page/section where the evolution of the policy is displayed thus a user can view the entire history of Guardian actions, switching to the 'old' version of the policy and seeing their artefacts in their trustchains. This view should clearly display different policy versions, and link to the 'policy diff' tool for a quick comparison view of what's changed between them.

### Definition of done
Users can browse trustchains of all versions of the selected policy, artefacts produced etc.

### Acceptance criteria
Trust chain visualisation contains views allowing users to see previous (and subsequent - if any) versions of the policy, navigate to their trustchains, and quickly switch to policy version diff.