errorutil: add benchmark for errors.Is

[rafiss]

This is to help debug an expensive error handling call path that was seen in a profile.

goos: darwin
goarch: arm64
cpu: Apple M1 Pro
=== RUN   BenchmarkErrorsIs
BenchmarkErrorsIs
=== RUN   BenchmarkErrorsIs/SimpleError
BenchmarkErrorsIs/SimpleError
BenchmarkErrorsIs/SimpleError         	 1618170	       716.0 ns/op	     448 B/op	      14 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/WrappedError
BenchmarkErrorsIs/WrappedError
BenchmarkErrorsIs/WrappedError        	  300048	      4009 ns/op	    3344 B/op	      67 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/WrappedWithStack
BenchmarkErrorsIs/WrappedWithStack
BenchmarkErrorsIs/WrappedWithStack    	  941736	      1179 ns/op	     896 B/op	      23 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/NetworkError
BenchmarkErrorsIs/NetworkError
BenchmarkErrorsIs/NetworkError        	  414190	      2790 ns/op	    1768 B/op	      52 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/DeeplyWrappedNetworkError
BenchmarkErrorsIs/DeeplyWrappedNetworkError
BenchmarkErrorsIs/DeeplyWrappedNetworkError         	   44353	     27774 ns/op	   23419 B/op	     381 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/MultipleWrappedErrors
BenchmarkErrorsIs/MultipleWrappedErrors
BenchmarkErrorsIs/MultipleWrappedErrors             	   65017	     18352 ns/op	   20259 B/op	     275 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/NetworkErrorWithLongAddress
BenchmarkErrorsIs/NetworkErrorWithLongAddress
BenchmarkErrorsIs/NetworkErrorWithLongAddress       	  111456	     10746 ns/op	    8145 B/op	     150 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/WithMessage
BenchmarkErrorsIs/WithMessage
BenchmarkErrorsIs/WithMessage                       	  520652	      2595 ns/op	    1880 B/op	      40 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/MultipleWithMessage
BenchmarkErrorsIs/MultipleWithMessage
BenchmarkErrorsIs/MultipleWithMessage               	  107244	      9438 ns/op	    6929 B/op	     122 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/WithMessageAndStack
BenchmarkErrorsIs/WithMessageAndStack
BenchmarkErrorsIs/WithMessageAndStack               	  215155	      5640 ns/op	    5296 B/op	      87 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/NetworkErrorWithMessage
BenchmarkErrorsIs/NetworkErrorWithMessage
BenchmarkErrorsIs/NetworkErrorWithMessage           	  184285	      6572 ns/op	    4648 B/op	      99 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/NetworkErrorWithEverything
BenchmarkErrorsIs/NetworkErrorWithEverything
BenchmarkErrorsIs/NetworkErrorWithEverything        	   25274	     46921 ns/op	   35885 B/op	     594 allocs/op
=== NAME
=== RUN   BenchmarkErrorsIs/DeeplyNested100Levels
BenchmarkErrorsIs/DeeplyNested100Levels
BenchmarkErrorsIs/DeeplyNested100Levels             	     256	   4702923 ns/op	 5931739 B/op	   62712 allocs/op
=== NAME

informs: #153772
Release note: None

[cockroach-teamcity]

This change is 

[rafiss]

Here's a cpu profile from running ./dev bench pkg/util/errorutil -f=BenchmarkErrorsIs/NetworkErrorWithEverything --test-args '-test.cpuprofile=cpu.pb.gz -test.cpu=4'. cpu.pb.gz

It shows some similarities to the one from the roachtest, but none of the net.(*OpError) formatting shows up: #153772 (comment)

[rafiss]

The benchmark is being moved to the errors repo: cockroachdb/errors#153