[N3] Any TX that has more than 1500 GAS in system fee will stuck in mempool

[vncoelho]

Describe the bug
Attach 1500+ GAS to a TX and relay it, let's say 1500,1 GAS

This TX will stuck in node's mem pool and cause problems and possible network stuck.

[vncoelho]

@roman-khimov @AnnaShaleva , can you try on neo-go?

[roman-khimov]

That's because of MaxBlockSystemFee. But node shouldn't allow this transaction to enter pool.

[roman-khimov]

Although in C# RPCs have no idea at all what this setting is. It should've been moved to Policy along with other things in Echidna, but it's not late to do this now as well.

[shargon]

MaxBlockSystemFee is defined in the plugin (DBft) and mempool is in the core. Maybe we should drop it from the plugin