feat: Add experimental feature for synchronous update calls

[DSharifi]

Description

This PR adds an experimental feature flag to support synchronous update calls, which are routed to /api/v3/.../call. The feature is opt in, and requires the user to also enable a flag in the builder of ReqwestTransport or HyperTransport.

Changes:

• Route provider no longer provides the /api/v2 prefix for routes.
• Added the feature flag experimental_sync_call, which enables a toggle to ReqwestTransport and HyperTransport to route ingress messages to the new v3 call endpoint.
• Agent no longer returns a RequestId for update calls, but an enum which either contains the response of the call or the underlying RequestId which can be used to poll the request status.

How Has This Been Tested?

Integration tests have been updated to expect requests are sent to v3/.../call.

Checklist:

• The title of this PR complies with Conventional Commits.
• I have edited the CHANGELOG accordingly.
• I have made corresponding changes to the documentation.

[DSharifi]

I changed the DFX version since CI would fail when it pulls the current latest stable,0.21, which uses a replica version that hasn't enabled the new endpoint for synchronous ingress messages.