use a type parameter for stream in EachLine, improves performance

[KristofferC]

From @martinholters idea in #19141 (comment)

function countchars(filename)
    io = open(filename, "r")
    c = 0
    for line in eachline(io, keep=true)
        c += length(line)
    end
    close(io)    
    c
end

@time countchars("PF00089.fasta")

File at https://raw.githubusercontent.com/diegozea/mitos-benchmarks/master/data/PF00089.fasta

Before:

0.255199 seconds (1.63 M allocations: 57.544 MiB, 0.66% gc time)

After:

0.064163 seconds (1.09 M allocations: 49.241 MiB, 5.91% gc time)

Julia 0.6

0.157770 seconds (1.63 M allocations: 99.056 MiB, 9.22% gc time)

[KristofferC]

Not sure this is tracked but might as well

@nanosoldier runbenchmarks(ALL, vs = ":master")

[nanosoldier]

Your benchmark job has completed - possible performance regressions were detected. A full report can be found here. cc @ararslan

[ararslan]

This line should be unindented one level as well.

[KristofferC]

I'll try fix it before merging with ci skip to not waste CI.

[JeffBezanson]

I think this should remain inside the struct block so we don't expose a 3-argument EachLine method.

[KristofferC]

Fixed

[martinholters]

While at it, we could consider also making the type of ondone a parameter. Not sure it's worth it.

[KristofferC]

I thought about it but it is only called once, right, so I felt that it probably wasn't needed.

[martinholters]

Same feeling here, just wanted to make sure it's at least considered.