fix: [PDI-3226] - Only show Maintenance Policy for Linodes that actually have a Maintenance Policy

[bnussman-akamai]

Description 📝

• Adds extra conditional logic to the Linode Details page to ensure the new "Maintenance Policy" value only shows when the Linode actually supports it
• Updates api-v4 types to reflect the API

Scope 🚢

Upon production release, changes in this PR will be visible to:

• All customers
• Some customers (e.g. in Beta or Limited Availability)
• No customers / Not applicable

Preview 📷

Before	After
A maintenance policy is showing even though this Linode does not have one	Now, no maintenance policy will show because the Linode does not have one

How to test 🧪

• Have a Linode on your account that a maintenance_policy of null and does not have Maintenance Policy in the capabilities array
  • I used Chrome's "Override Content" feature to mock this
• Verify the Maintenance Policy section does not show beside the Linode's status

Author Checklists

As an Author, to speed up the review process, I considered 🤔

👀 Doing a self review
❔ Our contribution guidelines
🤏 Splitting feature into small PRs
➕ Adding a changeset
🧪 Providing/improving test coverage
🔐 Removing all sensitive information from the code and PR description
🚩 Using a feature flag to protect the release
👣 Providing comprehensive reproduction steps
📑 Providing or updating our documentation
🕛 Scheduling a pair reviewing session
📱 Providing mobile support
♿ Providing accessibility support

• I have read and considered all applicable items listed above.

As an Author, before moving this PR from Draft to Open, I confirmed ✅

• All tests and CI checks are passing
• TypeScript compilation succeeded without errors
• Code passes all linting rules

[dwiley-akamai]

Verification steps ✅
Code review ✅
LinodeEntityDetail unit test passes locally & in CI ✅

[linode-gh-bot]

Cloud Manager UI test results

🎉 855 passing tests on test run #3 ↗︎

❌ Failing	✅ Passing	↪️ Skipped	🕐 Duration
0 Failing	855 Passing	11 Skipped	42m 5s