fix(pkg/ioutil):avoid panic in PageWriter.Write() when pageBytes is 0

[secsys-go]

pkg/ioutil: add check for pageBytes when creating PageWriter

NewPageWriter() without check could return a PageWriter whose pageBytes is equal to 0. This is fatal when buffer to write is longer than defaultBufferBytes, and it will crashed in PageWriter.Write() with: "panic: runtime error: integer divide by zero". This check will prevent creating PageWriter in NewPageWriter()when pageBytes is 0, and return a nil at that time.

[codecov-commenter]

Codecov Report

Merging #14022 (29d30ab) into main (b7be91f) will increase coverage by 0.02%. The diff coverage is 62.50%.

:exclamation: Current head 29d30ab differs from pull request most recent head 76112f1. Consider uploading reports for the commit 76112f1 to get more accurate results

@@            Coverage Diff             @@
##             main   #14022      +/-   ##
==========================================
+ Coverage   75.00%   75.03%   +0.02%     
==========================================
  Files         450      446       -4     
  Lines       37173    36723     -450     
==========================================
- Hits        27882    27555     -327     
+ Misses       7522     7432      -90     
+ Partials     1769     1736      -33     

Flag	Coverage Δ
all	75.03% <62.50%> (+0.02%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/watch_command.go	44.08% <0.00%> (ø)
server/etcdmain/etcd.go	41.25% <25.00%> (-4.12%)	:arrow_down:
server/etcdmain/config.go	86.12% <71.42%> (+0.85%)	:arrow_up:
etcdctl/ctlv3/command/txn_command.go	63.15% <100.00%> (-4.39%)	:arrow_down:
etcdctl/ctlv3/command/util.go	17.97% <100.00%> (ø)
client/pkg/v3/verify/verify.go	88.46% <0.00%> (-11.54%)	:arrow_down:
server/proxy/grpcproxy/register.go	81.39% <0.00%> (-9.31%)	:arrow_down:
server/auth/simple_token.go	80.00% <0.00%> (-8.47%)	:arrow_down:
server/etcdserver/api/v3lock/lock.go	61.53% <0.00%> (-8.47%)	:arrow_down:
etcdctl/ctlv3/command/printer_simple.go	53.08% <0.00%> (-8.03%)	:arrow_down:
... and 17 more

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[ahrtr]

Please also rebase this PR.

[ahrtr]

@secsys-go Please update this PR per the comment.

[ahrtr]

Please squash the commits.

[ahrtr]

Again, please squash the commits into just one commit. FYI. git-squash

[secsys-go]

This is the squashed one:dc559c17979a1823fab7c80478c74b4db28e0f1b

[ahrtr]

Since there is no response from the author for a long time, so I resolved it in https://github.com/etcd-io/etcd/pull/14452