increase MAX_READ_CHUNK from 100 to 255 to support more realistic path/command lengths

[nurturenature]

Hi,

I was testing possibly adding torn-seq and torn-op to Jepsen's jepsen.lazyfs Nemesis, and noticed that longer file paths were breaking command parsing:

[global] [info] [lazyfs.fifo]: running LazyFS...
[global] [info] [lazyfs.faults.worker]: waiting for fault commands...
[global] [info] [lazyfs.faults.worker]: received 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/config.toml::persist=[2]::occurr'
[global] [info] [lazyfs.faults.worker]: configured successfully 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/config.toml::persist=[2]::occurr'
[global] [info] [lazyfs.faults.worker]: command unknown 'nce=1'
[global] [info] [lazyfs.faults.worker]: received 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/control-db/conf::persist=[2]::oc'
[global] [info] [lazyfs.faults.worker]: configured successfully 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/control-db/conf::persist=[2]::oc'
[global] [info] [lazyfs.faults.worker]: command unknown 'urrence=1'
...

This PR increases MAX_READ_CHUNK from 100 to 255.
As any fixed # will be arbitrary, this seemed both adequate and reasonable.

After increasing MAX_READ_CHUNK, the build and tests continue to pass.
Rerunning the Jepsen tests shows successful command parsing:

[global] [info] [lazyfs.fifo]: running LazyFS...
[global] [info] [lazyfs.faults.worker]: waiting for fault commands...
[global] [info] [lazyfs.faults.worker]: received 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/config.toml::persist=[2]::occurrence=1'
[global] [info] [lazyfs.faults.worker]: configured successfully 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/config.toml::persist=[2]::occurrence=1'
[global] [info] [lazyfs.faults.worker]: received 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/control-db/conf::persist=[2]::occurrence=1'
[global] [info] [lazyfs.faults.worker]: configured successfully 'lazyfs::torn-seq::op=write::file=/root/.local/share/spacetime/data/control-db/conf::persist=[2]::occurrence=1'
...

and a torn-seq that was enough to unrecoverably crash the system being tested:

---

If you are willing to accept this PR, would you also be willing to create a new tag/release?

If so, I will work on adding torn-seq and torn-op support to Jepsen's jepsen.lazyfs Nemesis.

Also note that the current latest tag, 0.3.0, doesn't include the torn-seq and torn-op refactor, etc.

Thanks!