config: add 'config mac add/del' for static FDB entries

[AnantKishorSharma]

What I did

Added a config mac command group for static MAC (FDB) entries via CONFIG_DB:
config mac add <mac> <vlan> <interface> and config mac del <mac> <vlan>. Both write the
CONFIG_DB FDB table (consumed by vlanmgr, modeled by sonic-fdb.yang). Part of
config-driven static L2 forwarding — HLD sonic-net/SONiC#2468.

How I did it

Added the mac click group + add/del subcommands with MAC/VLAN/interface validation;
they set/clear the FDB table entry (Vlan, mac) → {port} in CONFIG_DB.

How to verify it

Unit tests tests/config_mac_test.py (add/del + validation). Hardware: config mac add/del
→ CONFIG_DB FDB → APPL FDB_TABLE → ASIC SAI_FDB_ENTRY_TYPE_STATIC; the target MAC is
forwarded to the configured port.

Previous command output (if the output of a command-line utility has changed)

N/A — new command.

New command output (if the output of a command-line utility has changed)

admin@sonic:~$ sudo config mac add 00:11:22:33:44:55 100 Ethernet72
admin@sonic:~$ sudo config mac del 00:11:22:33:44:55 100

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[mssonicbld]

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[mssonicbld]

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[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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