PR: Improve read performance and rewrite iseof

[andfoy]

This PR makes important changes to improve reading performance, as well as detecting if a process reached End-Of-Line.

[codecov-commenter]

Codecov Report

Merging #8 (da58d85) into main (e9886c1) will increase coverage by 2.54%.
The diff coverage is 68.62%.

❗ Current head da58d85 differs from pull request most recent head 4da0266. Consider uploading reports for the commit 4da0266 to get more accurate results

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   45.62%   48.16%   +2.54%     
==========================================
  Files           9       10       +1     
  Lines        1690     1823     +133     
==========================================
+ Hits          771      878     +107     
- Misses        919      945      +26     

Flag	Coverage Δ
unittests	48.16% <68.62%> (+2.54%)	⬆️

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Impacted Files	Coverage Δ
src/lib.rs	0.85% <ø> (ø)
src/pty.rs	64.63% <25.00%> (-2.46%)	⬇️
src/pty/winpty/pty_impl.rs	77.77% <25.00%> (-1.39%)	⬇️
tests/conpty.rs	71.33% <50.00%> (+20.65%)	⬆️
src/pty/conpty/pty_impl.rs	70.49% <52.94%> (-1.13%)	⬇️
src/pty/base.rs	70.53% <74.23%> (-3.08%)	⬇️
src/pty/winpty/bindings.rs	0.00% <0.00%> (ø)
... and 1 more

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