[Enhancement] DoAppend function of CommitLog class annotation optimize

[Qoozm]

Before Creating the Enhancement Request

• I have confirmed that this should be classified as an enhancement rather than a bug/feature.

Summary

This is a annotation optimize about CommitLog's doAppend function

Motivation

Hi Community！
As a newcomer, annotation is important for me to read and understand the code, when i was learned about store flow, i find there are some fuzzy annotation.

1. There are't explain of pos init
2. There are two problem
   1. The first 8 belong to PHYSICALOFFSET but SYSFLAG,, maybe we should add 8 to pos after line 1972
   2. "11 STORETIMESTAMP" annotation should at 1977
3. The UtilAll.crc32 function will change buffer's position index, add a annotation is more clear

Describe the Solution You'd Like

Here is my optimization plan.

Describe Alternatives You've Considered

no

Additional Context

No response