feat: add open telemetry instrumentation

[lucacasonato]

This commit adds some useful automatic instrumentation for when users are using --unstable-otel:

• Fresh renames the span for incoming HTTP requests to $METHOD $ROUTE and the http.route attribute is added.
• Fresh creates a span around FS route handlers, showing whether they returned a response or data.
• Fresh creates a span around async components, showing how long they took to execute.
• Fresh adds a span around preact rendering, showing how long rendering takes.
• Fresh adds a span around static file serving, showing how long it took and whether there were requests without a cache bust key.

We can improve this in the future with more telemetry, such as metrics.

[lucacasonato]

My previous PR accidentally removed all test dependencies from the lock file 😓

[marvinhagemeister]

LGTM