feat: As a user, I want to access log's buffer size can be configed in config file

[qihaiyan]

Description

As a user, I want to access log's buffer size can be configed in config file.
The buffer size is now hard coded in ngx_tpl.lua

Access log buffering can significantly reduce disk I/O and improve server performance. 
Enabling access log buffering is relatively simple in NGINX. To do this,
use the following directive in your NGINX configuration:

access_log /var/log/nginx/access.log main buffer=32k;
This directive tells NGINX to store the access log entries in a buffer of size 32k before writing them to the log file. 
Increasing the buffer size can minimize the number of write operations to the disk, resulting in improved performance.

[shreemaan-abhishek]

@qihaiyan would you like to submit a PR?

[qihaiyan]

@qihaiyan would you like to submit a PR?

OK