consensus/misc/eip4844: expose TargetBlobsPerBlock (#32991)

Rollups may want to use these to dynamically adjust blobs posted after
BPO forks.

Author: Tristan-Wilson

consensus/misc/eip4844/eip4844.go

@@ -200,6 +200,15 @@ func LatestMaxBlobsPerBlock(cfg *params.ChainConfig) int {
 	return bcfg.Max
 }
 
+// TargetBlobsPerBlock returns the target blobs per block for a block at the given timestamp.
+func TargetBlobsPerBlock(cfg *params.ChainConfig, time uint64) int {
+	blobConfig := latestBlobConfig(cfg, time)
+	if blobConfig == nil {
+		return 0
+	}
+	return blobConfig.Target
+}
+
 // fakeExponential approximates factor * e ** (numerator / denominator) using
 // Taylor expansion.
 func fakeExponential(factor, numerator, denominator *big.Int) *big.Int {