[format] fixed syslog regex

[Foalyy]

Some lines in my rsyslog log files on Debian (the ones coming from the imtcp module) were not matched properly because of slight differences in the format of some fields :

• the log_pid field sometimes contains a point
• the : after the PID is sometimes missing

Here is an example :
2025-04-21T12:24:51.761734+02:00 myhostname kernel [499130.569180] [UFW BLOCK] IN=enX0...

I'm not sure if these differences are due to a misconfiguration on my part. I'm using the latest version of rsyslog with this configuration :
$ActionFileDefaultTemplate RSYSLOG_FileFormat.

This pull requests offers to fix this on the regex's side in case other users have the same issue.

[Foalyy]

Related issue : rsyslog/rsyslog#4891

[tstack]

Can you also add the sample log line that was not matched into the format file.

[Foalyy]

Here is the line that I will add to the sample section of the json file, with a missing colon :
2025-04-15T17:36:24.135033+02:00 myhostname sshd[730594] Disconnected from authenticating user root 218.92.0.111 port 37632 [preauth]

Regarding the dot in the log_pid field, actually, I was mistaken by the missing colon. In my original example (kernel [499130.569180] [UFW BLOCK]) the colon is supposed to be after kernel and the numbers in brackets are part of the body, not log_pid. After looking further, I cannot find an example with a dot in the log_pid field. Would you prefer that I revert the [\\d\\.] in this pull request?

[tstack]

Would you prefer that I revert the [\d\.] in this pull request?

Yeah, leave that out for now.