* Rely on con_cache telemetry

Now that https://github.com/sasa1977/con_cache/pull/76
is released, we don't have to use low-level operations
to emit hit/miss events.

This PR also wraps cache processes with
a function returning appropriate child specs lists.

Ideally each cache will have its own supervisor/child specs
going forward. This is an intermediate step in that direction.

* Update lib/plausible/application.ex

Co-authored-by: Adrian Gruntkowski <adrian.gruntkowski@gmail.com>

* Declare caches without warmers with plain child specs

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Co-authored-by: Adrian Gruntkowski <adrian.gruntkowski@gmail.com>