sum of all mempool tx's fees (NOT modified fee)
Declared in <txmempool.h>
[[guarded_by(0x7f95135d0e88), guarded_by(0x7f9501b10268), guarded_by(0x7f950ec76458), guarded_by(0x7f9525ea61a8), guarded_by(0x7f95150958e8), guarded_by(0x7f9508269b88), guarded_by(0x7f94f856d298), guarded_by(0x7f9513c57488)]]
CAmount m_total_fee = {0};