refactor: Optimize markedReader.Read()

[nemith]

Read() was just looping over ReadByte(). Which was really fast but this is slighly faster and perhaps more correct by doing larger reads and bytes.IndexByte to search for the deliminator.

❯ go run golang.org/x/perf/cmd/benchstat@latest before.txt after.txt
goos: darwin
goarch: arm64
pkg: nemith.io/netconf/transport
cpu: Apple M4 Max
                               │  before.txt  │              after.txt               │
                               │    sec/op    │    sec/op     vs base                │
MarkedRead/Small_200B-16         17.02n ± ∞ ¹   15.96n ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Medium_128KB-16       16.67n ± ∞ ¹   16.12n ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Large_10MB-16         17.09n ± ∞ ¹   15.90n ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Small_200B-16     9.139n ± ∞ ¹   8.854n ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Medium_128KB-16   9.093n ± ∞ ¹   9.076n ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                          13.21n         12.69n        -3.99%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05

                               │  before.txt   │               after.txt               │
                               │      B/s      │      B/s       vs base                │
MarkedRead/Small_200B-16         11.27Gi ± ∞ ¹   12.02Gi ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Medium_128KB-16       7.152Ti ± ∞ ¹   7.394Ti ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Large_10MB-16         558.2Ti ± ∞ ¹   600.0Ti ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Small_200B-16     20.99Gi ± ∞ ¹   21.67Gi ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Medium_128KB-16   13.11Ti ± ∞ ¹   13.14Ti ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                          1.639Ti         1.707Ti        +4.16%
¹ need >= 6 samples for confidence interval at level 0.95
² need >= 4 samples to detect a difference at alpha level 0.05

                               │ before.txt  │              after.txt              │
                               │    B/op     │    B/op      vs base                │
MarkedRead/Small_200B-16         0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Medium_128KB-16       0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Large_10MB-16         0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Small_200B-16     0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Medium_128KB-16   0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                                    ³                +0.00%               ³
¹ need >= 6 samples for confidence interval at level 0.95
² all samples are equal
³ summaries must be >0 to compute geomean

                               │ before.txt  │              after.txt              │
                               │  allocs/op  │  allocs/op   vs base                │
MarkedRead/Small_200B-16         0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Medium_128KB-16       0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedRead/Large_10MB-16         0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Small_200B-16     0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
MarkedReadByte/Medium_128KB-16   0.000 ± ∞ ¹   0.000 ± ∞ ¹       ~ (p=1.000 n=1) ²
geomean                                    ³                +0.00%               ³
¹ need >= 6 samples for confidence interval at level 0.95
² all samples are equal
³ summaries must be >0 to compute geomean