Apply defaults in wait and analysis Stage Plugins

[rawadhossain]

What this PR does:
Applies defaults.Set() when decoding stage configurations in the wait and analysis stage plugins, ensuring default values are initialized correctly during config loading.

Why we need it:

• Stage plugins need to apply defaults during config decoding.
• wait and analysis were unmarshalled without calling defaults.Set().
• Hence config defaults were not being applied.

Part of Issue #6174

Does this PR introduce a user-facing change?:
No

• How are users affected by this change: Stage configurations now correctly apply default values when fields are omitted, as expected behavior.
• Is this breaking change: No
• How to migrate (if breaking change): N/A