smtp: Prevent error messages on packet path

[jlucovsky]

Continuation of #11520

Issue: 7126

This commit abandons the use of StringParseUint32 which generates an error message of there are non-numeric characters.

The SMTP parser had used this function on the packet path; this commit uses ByteExtractStringUint32 instead.

An example of the content causing the error message to be emitted:

3460 LAST

Link to ticket: https://redmine.openinfosecfoundation.org/issues/7126

Describe changes:

• Use ByteExtractStringUint32 instead of StringParseUint32 function that emits error messages

Updates:

• Commit message update explaining why strtoul must clear errno before invoking it.
• Added s-v test

Provide values to any of the below to override the defaults.

• To use an LibHTP, Suricata-Verify or Suricata-Update pull request, link to the pull request in the respective _BRANCH variable.
• Leave unused overrides blank or remove.

SV_REPO= SV_BRANCH=https://github.com/OISF/suricata-verify/pull/2010 SU_REPO= SU_BRANCH= LIBHTP_REPO= LIBHTP_BRANCH=