WIP: Add support for memory monitoring on Firebrick platform (#15021)

* Add support for Firebrick memory monitoring.

* Add mempool testing for Firebrick.

mibs/firebrick/FIREBRICK-GLOBAL-MIB

@@ -0,0 +1,61 @@
+-- *------------------------------------------------
+-- * Firebrick System Global Info MIB
+-- *
+-- * Feb 2023, David Honour
+-- *
+-- * Copyright (c) 2023 by Andrews & Arnold
+-- *------------------------------------------------
+
+FIREBRICK-GLOBAL DEFINITIONS ::= BEGIN
+
+IMPORTS
+    MODULE-IDENTITY,
+    OBJECT-TYPE,
+    NOTIFICATION-TYPE,
+    Gauge32,
+    MODULE-COMPLIANCE,
+    OBJECT-GROUP,
+    NOTIFICATION-GROUP
+        FROM SNMPv2-CONF
+    TEXTUAL-CONVENTION,
+    enterprises
+        FROM RFC1155-SMI
+    DisplayString
+        FROM SNMPv2-TC
+    firebrickNewStyle
+        FROM FIREBRICK-MIB
+        ;
+
+fbGlobalMib MODULE-IDENTITY
+    LAST-UPDATED "202302170000Z"
+    ORGANIZATION "Andrews & Arnold Limited"
+    CONTACT-INFO
+        "Andrews & Arnold
+        Unit 1&2, Enterprise Court
+        Bracknell, Berkshire, RG12 1QS
+        United Kingdom
+
+        Tel: +44 3333 400 999
+        Email: support@aa.net.uk"
+    DESCRIPTION "System wide status"
+    REVISION "202302170000Z"
+    DESCRIPTION "Add memory usage"
+    ::= { firebrickNewStyle 4 }
+
+fbGlobalMemory OBJECT IDENTIFIER ::= { fbGlobalMib 1 }
+
+fbTotalMem OBJECT-TYPE
+    SYNTAX Gauge32
+    MAX-ACCESS read-only
+    STATUS current
+    DESCRIPTION "Total RAM (KiB)"
+    ::= { fbGlobalMemory 1 }
+
+fbFreeMem OBJECT-TYPE
+    SYNTAX Gauge32
+    MAX-ACCESS read-only
+    STATUS current
+    DESCRIPTION "Free RAM (KiB)"
+    ::= { fbGlobalMemory 2 }
+
+END