rm: make controller config metadata update atomic

[okJiang]

Development Task

Follow-up from PR #10246 review discussion: #10246 (comment)

Background:
POST /resource-manager/api/v1/config/controller currently validates controller-config keys before applying updates, but value/type validation and persistence still happen one field at a time through UpdateControllerConfigItem. If a request mixes one valid field with another invalid field, an earlier field may already have been persisted before the API returns 400.

This means the API is not fully all-or-nothing from the caller's perspective, even though the current test naming and review discussion expect atomic behavior.

This task is split out from PR #10246 as a follow-up instead of blocking that PR.

Expected work:

• make controller config metadata updates atomic from the API perspective
• avoid partial persistence when one field in a multi-field request is invalid
• add regression coverage for mixed valid/invalid payloads, such as a valid boolean field plus an invalid duration value