sum of all mempool tx's fees (NOT modified fee)
Declared in <txmempool.h>
[[guarded_by(0x7fd7537b8198), guarded_by(0x7fd74eec4b28), guarded_by(0x7fd75e706178), guarded_by(0x7fd759892948), guarded_by(0x7fd75ce04918), guarded_by(0x7fd759f6dda8), guarded_by(0x7fd75b82dfe8), guarded_by(0x7fd73e8ac248)]]
CAmount m_total_fee = {0};