core: types: less allocations when hashing and tx handling (#21265)

* core, crypto: various allocation savings regarding tx handling

* core: reduce allocs for gas price comparison

This change reduces the allocations needed for comparing different transactions to each other.
A call to `tx.GasPrice()` copies the gas price as it has to be safe against modifications and
also needs to be threadsafe. For comparing and ordering different transactions we don't need
these guarantees

* core: added tx.GasPriceIntCmp for comparison without allocation

adds a method to remove unneeded allocation in comparison to tx.gasPrice

* core/types: pool legacykeccak256 objects in rlpHash

rlpHash is by far the most used function in core that allocates a legacyKeccak256 object on each call.
Since it is so widely used it makes sense to add pooling here so we relieve the GC.
On my machine these changes result in > 100 MILLION less allocations and > 30 GB less allocated memory.

* reverted some changes

* reverted some changes

* trie: use crypto.KeccakState instead of replicating code

Co-authored-by: Martin Holst Swende <martin@swende.se>

eth/gasprice/gasprice.go

@@ -156,7 +156,7 @@ type transactionsByGasPrice []*types.Transaction
 
 func (t transactionsByGasPrice) Len() int           { return len(t) }
 func (t transactionsByGasPrice) Swap(i, j int)      { t[i], t[j] = t[j], t[i] }
-func (t transactionsByGasPrice) Less(i, j int) bool { return t[i].GasPrice().Cmp(t[j].GasPrice()) < 0 }
+func (t transactionsByGasPrice) Less(i, j int) bool { return t[i].GasPriceCmp(t[j]) < 0 }
 
 // getBlockPrices calculates the lowest transaction gas price in a given block
 // and sends it to the result channel. If the block is empty, price is nil.