Recent rejects backport to v0.11 #6750

(cherry picked from commit bbe41088c61f2ad328766e851ffe6169aa80935a)

(cherry picked from commit a3d65fedaa18686f0cc007d0a13dba6545250300)

While CBloomFilter is usually used with an explicitly set nTweak,
CRollingBloomFilter is only used internally. Requiring every caller to
set nTweak is error-prone and redundant; better to have the class handle
that for you with a high-quality randomness source.

Additionally when clearing the filter it makes sense to change nTweak as
well to recover from a bad setting, e.g. due to insufficient randomness
at initialization, so the clear() method is replaced by a reset() method
that sets a new, random, nTweak value.

(cherry picked from commit d2d7ee0e863b286e1c9f9c54659d494fb0a7712d)

(cherry picked from commit d741371d7d27e228aa64c618c50b23fb5449c3e1)

Nodes can have divergent policies on which transactions they will accept
and relay.  This can cause you to repeatedly request and reject the same
tx after its inved to you from various peers which have accepted it.
Here we add rolling bloom filter to keep track of such rejections,
clearing the filter every time the chain tip changes.

Credit goes to Alex Morcos, who created the patch that this code is
based on.

Original code by Peter Todd. Refactored to not construct the
filter at startup time by Pieter Wuille.

(cherry picked from commit 0847d9cb5fcd2fdd5a21bde699944d966cf5add9)

This avoids that premature return in the condition that a new chain is initialized
results in NULL pointer errors due to recentReject not being constructed.

Also add assertions where it is used.

(cherry picked from commit a8d0407c4fcf7c4e8ed0e8edabd204f7a4efa477)