Process KDUMP attributes in CFG_DB on init

[arista-nwolfe]

Fixes: sonic-net/sonic-buildimage#21625

Confirmed that with this change I see the values in config_db.json propagated to the kernel arguments on init.

E.G.

• Write KDUMP|config enabled="true" in config_db.json
• Reboot box
• I now see the expected operational output Ready after reboot

root@nfc406-7:~# sonic-db-cli CONFIG_DB hgetall "KDUMP|config"
{'enabled': 'true', 'memory': '0M-2G:256M,2G-4G:320M,4G-8G:384M,8G-:448M', 'num_dumps': '3'}

root@nfc406-7:~# show kdump config
Kdump administrative mode: Enabled
Kdump operational mode: Ready after reboot

• If I do one more reboot it now becomes ready

root@nfc406-7:~# show kdump config
Kdump administrative mode: Enabled
Kdump operational mode: Ready

[mssonicbld]

/azp run

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[mssonicbld]

/azp run

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