split up otel config into user configurable and runtime configurable
parts. user configurable part is now set via env vars parsed according
to the otel spec. otel is now enabled via `OTEL_DENO=true`, and
`--unstable-otel` only acts as a guard.
Fixes: https://github.com/denoland/deno/issues/27273
`SafeMap` treats its argument as an object with a "length" and index
properties, rather than a generic iterator, so every time we cloned it,
it was dropping all the data.
