[4 / 5] Make approval-voting runnable on a worker thread (#4846)

This is part of the work to further optimize the approval subsystems, if
you want to understand the full context start with reading
https://github.com/paritytech/polkadot-sdk/pull/4849#issue-2364261568,

# Description
This PR contain changes to make possible the run of single
approval-voting instance on a worker thread, so that it can be
instantiated by the approval-voting-parallel subsystem.

This does not contain any functional changes it just decouples the
subsystem from the subsystem Context and introduces more specific trait
dependencies for each function instead of all of them requiring a
context.

This change can be merged  independent of the followup PRs.

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Signed-off-by: Alexandru Gheorghe <[email protected]>
Co-authored-by: Andrei Sandu <[email protected]>