feat: correctly set HTTP route for UI requests

[sissbruecker]

Description

Attempts to set the correct route for HTTP root spans for Flow UI requests.

The HTTP root span is modified as such:

• Update the span name to contain the route template, without parameter values
• Update the semantic http.route attribute to contain the route template, without parameter values
• Update the semantic http.target attribute to contain the URL path with actual parameter values

These cases should be covered:

• [x] Javascript UI bootstrap - seems to cover client-side navigation or page loads
• [x] Set current UI - seems to cover UI synchronization / event requests

Additional cases can be covered in follow-up PRs.

Closes #2