Allow safe/finalized for eth_getLogs

[adytzu2007]

No description provided.

[adytzu2007]

This fixes issue #8454

[AskAlexSharov]

i think better change from -2 to -4 (or -5) , instead of removing validation at all

[adytzu2007]

Hey @AskAlexSharov, I checked and the unmarshal code doesn't allow explicit negative numbers so the only way to get a negative number in this code would be due to a symbolic name such as "safe".
Also, if GetBlockNumber gets a negative number smaller than -5 it seems that it would treat it as an uint64 so it would become a very big number and fail when trying to read the hash for it. Should I add a check here that number.Int64() is positive instead?

[AskAlexSharov]

@adytzu2007 what geth does in this case? we may do something compatible if it's good

[adytzu2007]

AFAICT, geth doesn't run any other validation on the block number in GetLogs once it unmarshals it from JSON. It also doesn't support latestExecuted and requires a hex number instead of also accepting an unsigned number.

[yperbasis]

Please remove now unused "math/big" from the import