IOSXR ShowPlatform: tolerate missing config_state; relax <plim> spacing

[bleuzkernel]

Description

This PR fixes the IOSXR ShowPlatform parser to correctly handle lines where the Config state column is absent and to accept variable spacing before the PLIM field.

Motivation and Context

Some IOS XR platforms (e.g., ASR 9903) produce show platform output lines without the Config state column for certain nodes/modules. Example line that previously failed to match and was skipped:

0/0/1             A9903-20HG-PEC             OK

By relaxing whitespace before <plim> and making <config_state> optional, the parser now:

• Correctly parses such lines instead of skipping them.
• Remains backward compatible with outputs that include config state.
• This improves robustness across XR releases and hardware variants, preventing partial/incomplete parse results.

Impact (If any)

Negative impact: None expected.

• No schema changes.
• Existing outputs continue to parse identically.
• Expanded matching is limited to valid whitespace and optional tail field; risk of false positives is minimal.

Screenshots

Reproducer (raw device output)

RP/0/RP0/CPU0:Router#show platform
Thu Sep 11 10:42:18.531 GMT+6
Node              Type                       State             Config state
--------------------------------------------------------------------------------
0/RP0/CPU0        A99-RP-F(Active)           IOS XR RUN        NSHUT
0/RP1/CPU0        A99-RP-F(Standby)          IOS XR RUN        NSHUT
0/FT0             ASR-9903-FAN               OPERATIONAL       NSHUT
0/FT1             ASR-9903-FAN               OPERATIONAL       NSHUT
0/FT2             ASR-9903-FAN               OPERATIONAL       NSHUT
0/FT3             ASR-9903-FAN               OPERATIONAL       NSHUT
0/0/CPU0          ASR-9903-LC                IOS XR RUN        NSHUT
0/0/1             A9903-20HG-PEC             OK
0/PT0             ASR-9900-DC-PEM            OPERATIONAL       NSHUT

Problem (before)

The parser skipped subslot entries that omit the Config state column, e.g.:

0/0/1 A9903-20HG-PEC OK

As a result, subslot cards were absent from the parsed structure (even in golden_output9_output.txt).

Before (parsed output excerpt):

{
  "lc": {
    "0/0": {
      "name": "ASR-9903-LC",
      "full_slot": "0/0/CPU0",
      "state": "IOS XR RUN",
      "config_state": "NSHUT"
    }
  }
}

Fix

Relax whitespace before <plim> from a single space to \s+.
Make <config_state> optional to accommodate lines without that column.
This enables parsing of subslot lines like 0/0/1 ... OK.

Result (after)

After (parsed output excerpt):

{
  "lc": {
    "0/0": {
      "name": "ASR-9903-LC",
      "full_slot": "0/0/CPU0",
      "state": "IOS XR RUN",
      "config_state": "NSHUT",
      "subslot": {
        "1": {
          "name": "A9903-20HG-PEC",
          "state": "OK",
          "config_state": null,
          "redundancy_state": null
        }
      }
    }
  }
}

Tests

Existing golden outputs remain valid.

Added golden_output10* to cover the missing config state subslot case shown above.

Checklist

• I have updated the changelog.
• I have updated the documentation (If applicable).
• I have added tests to cover my changes (If applicable).
• All new and existing tests passed.
• All new code passed compilation.