Persistent slot ID support

[tasleson]

Slot identifiers today are assigned at discovery time, so they can shift
across boots or hot-plug events. This makes it hard for callers to track
a drive once it becomes unresponsive or the kernel drops it.

Two public functions added.

1. bool led_slot_persistent_id_support(struct led_ctx *ctx, enum led_cntrl_type cntrl)

   Which simply returns true if persistent ID support exists for the
   controller type

2. char *led_slot_persistent_id(struct led_slot_list_entry *se)

   Which returns the persistent slot ID or NULL on non-existence or error

The existing slot ID function is left untouched to avoid breaking code
that may rely on its value.

Rudimentary testing has been done on a single SES equipped hardware system.
SES leverages an enclosure ID for creating the SES persistent ID.

TODO: investigate implementing persistent IDs for other transport layers
that expose the slots API.

[github-actions]

Hey @tasleson, a file(s) you own were modified in this PR! Could you take a look?

---

Caused by:

• src/lib/ses.c
• src/lib/ses.h
• src/lib/smp.c
• src/lib/smp.h

[github-actions]

Hey @nfont, a file(s) you own were modified in this PR! Could you take a look?

---

Caused by:

• src/lib/amd.c
• src/lib/amd.h
• src/lib/amd_ipmi.c
• src/lib/amd_sgpio.c
• src/lib/amd_sgpio.h

[github-actions]

Hey @prabhakar, a file(s) you own were modified in this PR! Could you take a look?

---

Caused by:

• src/lib/dellssd.c
• src/lib/dellssd.h

[bkucman]

Hi,
I'm ok with this change, just some minor tweaks to make.

[tasleson]

Thanks for the review. Any suggestions on adding this for different controller types?

[mtkaczyk]

HI @tasleson,
I don't see it integrated with ledctl, am I correct?

LGTM, to me but I would split it into two PRs first with fixes, the second with feature.

[tasleson]

HI @tasleson,
I don't see it integrated with ledctl, am I correct?

You are correct. This change is intended for software that is managing storage over time and controlling LEDs. I don't think users that are interactively using ledctl would necessarily need this, but we could certainly add it if others think it's useful.

[tasleson]

@mtkaczyk I broke this into 2 pull requests, the other is #269 which needs to be commited before this one.

[tasleson]

@bkucman I'll fix this PR up today.

[bkucman]

Hi @tasleson,
LGTM, since Mariusz also didn't report any corrections to the code, I'm merging this change :)

[bkucman]

For now, I don't see a need to extend this feature to other controllers. If anyone would like to extend this feature to other controllers, please do so in a new PR.