perf: improve error handling

[florianl]

Skip the reflectlite.TypeOf(target).Comparable() call that errors.Is() makes unconditionally on entry. As forwardReader.Read and reverseReader.Read return the io.* errors directly and never wrap them, avoid the costs of reflectlite.TypeOf().

$ benchstat main.txt new.txt 
goos: linux
goarch: amd64
pkg: github.com/cilium/ebpf/perf
cpu: 12th Gen Intel(R) Core(TM) i7-12700H
                 │  main.txt   │           new.txt           │
                 │   sec/op    │   sec/op     vs base        │
ReadRecordEOR-20   8.967n ± 0%   6.527n ± 0%  -27.21% (n=50)

                 │  main.txt  │            new.txt             │
                 │    B/op    │    B/op     vs base            │
ReadRecordEOR-20   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=50) ¹
¹ all samples are equal

                 │  main.txt  │            new.txt             │
                 │ allocs/op  │ allocs/op   vs base            │
ReadRecordEOR-20   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=50) ¹
¹ all samples are equal