fix: edge case divide by zero

[prestwich]

Fixes an edge case in fee history endpoint that results in invalid serialization.

• if gaslimit is 0, there's a divide-by-zero in the fee history endpoint
• IEEE754 specifies division by 0.0 to yield infinity (or -infinity for -0.0)
• serde_json serializes infinity as null
• serde_json cannot deserialize null to infinity
• in this weird edge case, reth can produce serialized FeeHistory structs that cannot be deserialized

It may seem like this would never occur as blocks cannot have a 0 limit in real life, but genesis files sometimes use 0 placeholders for gas limit, so this would be triggered on fresh nodes using such a genesis

Fix is to check for infinite values and set ratio to 1.0
NaN values are ruled out by casting from an integer

[Rjected]

oof, fix looks good though