e2e: nothing catches actor metric continuity across suspend/resume #1036

#761 reported that an actor's own counters merge and inflate across a suspend/resume, silently.
Everything in internal/e2e is platform plane, where we own the emitter, and we don't have coverage for workload emitted telemetry today.

So I'd like a small test where an actor increments a counter, we suspend and resume it, and we assert the total afterwards is a sum of what the actor actually counted rather than a reset artifact.

It would be nice to have this while we are designing #853 as

• behaviour-wise this is what we want, regardless of the final relay design
• it can help validating our relay design

Note: this will fail today, but that's the point. We probably want to mark it as optional until the relay lands, what do you all think?

High level idea:

• a tiny actor that counts something and exports otlp. The demo in demos: add actor telemetry continuity reference demo (#503) #750 may already give us this, and I'd rather not build a second one
• assert on the delta across the lifecycle operation, not on an absolute value

cc Da Huang (@git286) Jeff Luo (@JeffLuoo) Sanskar Singh Bhardwaj (@sanskar-singh-2403) Max Smythe (@maxsmythe)