Rationale:
Before this commit, the internal loop exited if:
- the expected amount of peers is found, or,
- the iterator returns `false` (exhaustion), or
- `batchSize` iterations are done.
The issue with the iterations count is, in case not enough
peer are found AND `iterator.Next` always returns `true`,
we don't control WHEN the loop is going to stop.
The root cause is we don't control the time needed to
run the `iterator.Next` function, which is a function of
`devp2P (geth)`.
The value of `batchSize (2000)` was chosen arbitrarily.
It turns out the time needed to run `iterator.Next` can go from a few micro seconds to a few hundreds of milliseconds.
==> In small networks (example: E2E tests), it was possible for the loop not to exit during several dozen of seconds.
With this commit, we replace the `batchSize` by a `batchPeriod`, ensuring the loop will never
run longer than `batchPeriod`, even in a small network.
Co-authored-by: Nishant Das <[email protected]>
