WeightInfo for System, Timestamp, and Utility (#6868)

* initial updates to system

* fix compile

* Update writer.rs

* update weights

* finish system weights

* timestamp weights

* utility weight

* Fix overflow in weight calculations

* add back weight notes

* Update for whitelisted benchmarks

* add trait bounds

* Revert "add trait bounds"

This reverts commit 12b08b7189aa3969f96fa19b211a370860fdb240.

* Update weights for unaccounted for read

substrate/utils/frame/benchmarking-cli/src/writer.rs

@@ -107,6 +107,12 @@ pub fn write_results(batches: &[BenchmarkBatch]) -> Result<(), std::io::Error> {
 				 VERSION,
 			)?;
 
+			// allow statements
+			write!(
+				file,
+				"#![allow(unused_parens)]\n#![allow(unused_imports)]\n\n",
+			)?;
+
 			// general imports
 			write!(
 				file,