fix(ARTESCA-17607): fix Rubrik bucket name UX issues (points 2-6)

[damiengillesscality]

Summary

Fixes points 2–6 from ARTESCA-17607 — UX issues on the bucket name field and form validation in the Rubrik ISV assistant.

• Point 2 — Error message discrepancy: {N} in the Joi message string was treated as a Joi template variable and resolved to empty, producing "must end with -rubrik-". Replaced with literal <number> in both string.min and string.pattern.name messages.
• Point 3 — Help text visibility: Wired helpText from fieldOverrides.bucketName through buildFields → BucketArrayField → BucketField → FormGroup.help so the format requirement renders as visible text below the field instead of being hidden behind the IconHelp tooltip.
• Point 4 — Tooltip font size: Wired tooltip from fieldOverrides.bucketName through the same chain so the platform-specific tooltip (using ListItem, consistent with other fields) is used instead of the fallback plain <Text> tooltip.
• Point 5 — "an unique": Fixed "Choose an unique name" → "Choose a unique name" in defaultBucketNameTooltip.
• Point 6 — Immutable Backup help text: Updated to "Enables object lock on the bucket, making backups permanent and unchangeable.".

Test plan

• In the Rubrik ISV assistant, enter a bucket name shorter than 3 chars — error should read Bucket name must end with -rubrik-<number> (e.g. my-archive-rubrik-0)
• Enter a bucket name without the -rubrik-<N> suffix — same error message
• Verify helper text Must end with -rubrik-<number> (e.g. my-archive-rubrik-0) is visible below the bucket name field without opening any tooltip
• Verify the tooltip font matches other fields (uses ListItem structure)
• Check the Immutable Backup toggle shows the updated helper text
• Run unit tests: npx jest --testNamePattern="rubrik|Rubrik"

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