enh(plugin): added 64 bits counters in snmp_standard::memory

[omercier]

Description

Added an option to switch to 64bits counters for memory. Default is to stick with 32 bits (this mode is used by several plugins, so it would be unsafe to change the default behaviour).

REFS: CTOR-542

Type of change

• [ ] Patch fixing an issue (non-breaking change)
• [ ] New functionality (non-breaking change)
• [x] Functionality enhancement or optimization (non-breaking change)
• [ ] Breaking change (patch or feature) that might cause side effects breaking part of the Software

How this pull request can be tested ?

Robot tests have been added.

Checklist

• [x] I have followed the coding style guidelines provided by Centreon
• [x] I have commented my code, especially hard-to-understand areas of the PR.
• [x] I have rebased my development branch on the base branch (develop).
• [ ] In case of a new plugin, I have created the new packaging directory accordingly.
• [x] I have implemented automated tests related to my commits.
• [x] I have reviewed all the help messages in all the .pm files I have modified.
  • [x] All sentences begin with a capital letter.
  • [x] All sentences are terminated by a period.
  • [x] I am able to understand all the help messages, if not, exchange with the PO or TW to rewrite them.
• [ ] After having created the PR, I will make sure that all the tests provided in this PR have run and passed.