Merge bitcoin/bitcoin#32154: fuzz: Avoid integer sanitizer warnings in policy_estimator target

fa6a007b8e fuzz: Avoid integer sanitizer warnings in policy_estimator target (MarcoFalke)

Pull request description:

  It seems odd to write a fuzz target to trigger integer sanitizer warnings in `CBlockPolicyEstimator::processBlockTx` and then suppress them. If the scenario can happen in reality, the code should be properly fixed to handle the cases. If not, it seems better to fix the fuzz target to not trigger meaningless traces.

  Do that here by keeping track of the current height and limiting mempool entries to at most this entry height.

ACKs for top commit:
  brunoerg:
    ACK fa6a007b8e
  dergoegge:
    utACK fa6a007b8e

Tree-SHA512: 2092017dc309fb095fe5d43cfb76efb691795f303d567ee919be2b5cac19a944293636229903dc4d1e8b9fe5daf9dc3058544321eff1735f91f804c3baa36cd0

test/sanitizer_suppressions/ubsan

@@ -53,13 +53,11 @@ unsigned-integer-overflow:CompressAmount
 unsigned-integer-overflow:DecompressAmount
 unsigned-integer-overflow:crypto/
 unsigned-integer-overflow:MurmurHash3
-unsigned-integer-overflow:CBlockPolicyEstimator::processBlockTx
 unsigned-integer-overflow:TxConfirmStats::EstimateMedianVal
 unsigned-integer-overflow:prevector.h
 unsigned-integer-overflow:InsecureRandomContext::rand64
 unsigned-integer-overflow:InsecureRandomContext::SplitMix64
 unsigned-integer-overflow:bitset_detail::PopCount
-implicit-integer-sign-change:CBlockPolicyEstimator::processBlockTx
 implicit-integer-sign-change:SetStdinEcho
 implicit-integer-sign-change:compressor.h
 implicit-integer-sign-change:crypto/