[lspci] Fix handling of more than one PCIe root port (#1822)

Summary:
I'm guessing most machines only have one PCIe root port, but things like ARM hosts tend to have more, and that breaks as it creates collisions.

As we want to keep backwards compatibility, and `lspci` is run with the defaults that doesn't show the root port if it's `0000`, only add it when it's non-zero, and also add it as a new extra field called `root_port` to denote the fact that there is one (useful when using the BDF to find files on disk, as when there is no `root_port`, one needs to add the extra `0000:`.

More detailed explanation I wrote on the slack channel:
On Linux, we run `lspci -vnnmk`, which will show the BDF in the first `Device:` field. So the first bug is that the regular expression on https://github.com/chef/ohai/blob/main/lib/ohai/plugins/linux/lspci.rb#L54 is missing a `\` before the `.`, therefore will will match `0001:02:03.4` as `01:02:03` which is plain broken. But fixing that we end up with `02:03.4` which is also plain wrong as it loses the root complex.
I see a few ways we could fix this:

1. Highly disruptive: we add -D to lspci, which means we'll always get the root complex even when it's 0000 . This is terrible 'cause it will basically break everything
2. We do this but only with an option in ohai. Less terrible, but means people have to know about that option
3. We do this but only when we notice more than one root complex. That's not really doable
4. We add a new field, root_complex in the PCI structure, which is 0000 by default and the actual root complex for everything else

I like 4 the most, as it mirrors closely what lspci does (https://github.com/pciutils/pciutils/blob/master/lspci.c#L285)
or maybe 5. We do it the same way lspci does it: if the root complex is 0, we just store the BDF as the ID, if it's not, we store the root complex + BDF
we can't really do 4 'cause we might have collisions... Like if you have 0000:01:02.3 and 0001:01:02.3 then they have to be stored differently. So we can either do:
Option A: 01:02.3 and 0001:01:02.3 (this can co-exist with everything today)
Option B: 00000:1:02.3 and 0001:01:02.3 (this most likely needs to become pci2)

Test Plan:
Before:
```
$ ohai | jq .pci\|keys
[
  "00:00.0",
  "01:00.0",
  "01:00.1",
  "02:00:0",
  "04:00:0",
  "08:00:0",
  "08:01:0",
  "08:02:0",
  "08:03:0",
  "08:04:0",
  "08:05:0",
  "09:00:0",
  "09:01:0"
]
```

After:
```
$ ohai | jq .pci\|keys
[
  "0002:00:00.0",
  "0004:00:00.0",
  "0008:00:00.0",
  "0008:01:00.0",
  "0008:02:01.0",
  "0008:02:02.0",
  "0008:03:00.0",
  "0008:04:00.0",
  "0008:05:00.0",
  "0009:00:00.0",
  "0009:01:00.0",
  "00:00.0",
  "01:00.0",
  "01:00.1"
]
```

Reviewers: jaymzh

Closes: #1693

Signed-off-by: Olivier Raginel <babar@meta.com>

lib/ohai/plugins/linux/lspci.rb

@@ -51,10 +51,14 @@ def standard_array(devices, d_id, tag, line)
 
       case dev[0]
       when "Device" # There are two different Device tags
-        if ( tmp = dev[1].match(/(#{hh}:#{hh}.#{h})/) )
+        if ( tmp = dev[1].match(/(#{hhhh}:)?(#{hh}:#{hh}\.#{h})/) )
           # We have a device id
           d_id = tmp[0] # From now on we will need this id
           devices[d_id] = Mash.new
+          if tmp[1]
+            # We have a root complex
+            devices[d_id]["root_port"] = tmp[1][0..-2]
+          end
         else
           standard_form(devices, d_id, hhhh, "device", dev[1])
         end

spec/unit/plugins/linux/lspci_spec.rb

@@ -86,6 +86,14 @@
       Driver:	nvme
       Module:	nvme
       NUMANode:	0
+
+      Device:	0005:00:00.0
+      Class:  PCI bridge [0604]
+      Vendor: Intel Corporation [8086]
+      Device: C620 Series Chipset Family PCI Express Root Port #1 [a190]
+      Rev:    f9
+      Driver: pcieport
+      NUMANode:       0
     LSPCI
     allow(plugin).to receive(:shell_out).with("lspci -vnnmk").and_return(
       mock_shell_out(0, @stdout, "")
@@ -96,7 +104,7 @@
     it "lists all devices" do
       plugin.run
       expect(plugin[:pci].keys).to eq(
-        ["00:1f.3", "00:1f.4", "00:1f.6", "02:00.0", "04:00.0", "05:00.0"]
+        ["00:1f.3", "00:1f.4", "00:1f.6", "02:00.0", "04:00.0", "05:00.0", "0005:00:00.0"]
       )
     end
 
@@ -129,5 +137,11 @@
       expect(plugin[:pci]["04:00.0"]["driver"]).to eq(["iwlwifi"])
       expect(plugin[:pci]["04:00.0"]["module"]).to eq(["iwlwifi"])
     end
+
+    it "populates the root port field" do
+      plugin.run
+      expect(plugin[:pci]["0005:00:00.0"]["driver"]).to eq(["pcieport"])
+      expect(plugin[:pci]["0005:00:00.0"]["root_port"]).to eq("0005")
+    end
   end
 end