Fix v1.5→v1.7 keystore migration: wrap symmetric-key in key-type container

[Copilot]

Description

The migration script transformed infix-keystore:cleartext-key to infix-keystore:symmetric-key at the wrong schema level, causing libyang validation errors for WiFi PSK configurations.

The YANG schema requires symmetric-key under a key-type choice (infix-keystore.yang:60-81), but the migration placed it directly under symmetric-key node.

Before (incorrect):

{
  "name": "hemma",
  "infix-keystore:symmetric-key": "password123"
}

After (correct):

{
  "name": "hemma",
  "key-type": {
    "infix-keystore:symmetric-key": "password123"
  }
}

Updated jq transformation in 1.7/20-keystore-cleartext-key-rename.sh to add the key-type container wrapper.

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe):

Original prompt

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This section details on the original issue you should resolve

<issue_title>Fails to migrate from confd v1.5 => v1.7</issue_title>
<issue_description>### Current Behavior

With wifi psk: Unclear reason, needs to be checked before release.

Nov  4 10:56:02 infix load[3920]: Loading startup-config ...
Nov  4 10:56:02 infix startup[3920]: libyang error: Node "cleartext-key" not found as a child of "symmetric-key" node. (/ietf-keystore:keystore/symmetric-keys/symmetric-key[name='hemma'])

Expected Behavior

No error

Steps To Reproduce

No response

Additional information

No response</issue_description>

<agent_instructions>I need your help to review the syntax migration scripts in src/confd/share/migrate/ to ensure they actually support migrating from v1.5 syntax to the latest.

I do not expect you to find any issue with this, it's purely review.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Fails to migrate from confd v1.5 => v1.7 #1369

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