eth, miner: add RPC method to modify miner gaslimit (pre london: ceiling) (#23134)

miner/miner.go

@@ -204,6 +204,12 @@ func (miner *Miner) SetEtherbase(addr common.Address) {
 	miner.worker.setEtherbase(addr)
 }
 
+// SetGasCeil sets the gaslimit to strive for when mining blocks post 1559.
+// For pre-1559 blocks, it sets the ceiling.
+func (miner *Miner) SetGasCeil(ceil uint64) {
+	miner.worker.setGasCeil(ceil)
+}
+
 // EnablePreseal turns on the preseal mining feature. It's enabled by default.
 // Note this function shouldn't be exposed to API, it's unnecessary for users
 // (miners) to actually know the underlying detail. It's only for outside project