core/txpool: remove "local" notion from the txpool price heap (#21478)

* core: separate the local notion from the pricedHeap

* core: add benchmarks

* core: improve tests

* core: address comments

* core: degrade the panic to error message

* core: fix typo

* core: address comments

* core: address comment

* core: use PEAK instead of POP

* core: address comments
# Conflicts:
#	core/tx_list.go
#	core/tx_pool.go