feat(deriv_auth)!: [TRHM-855] Add ability to support feature flag toggles by passing their widgets

[zohreh-deriv]

Clickup link: https://app.clickup.com/t/20696747/TRHM-855
Fixes issue: #

This PR contains the following changes:

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

Developers Note (Optional)

To support adding feature flags to the setting page, we will be able to pass two nullable widget to the deriv-setting_layout.dart.
One for under-development features and the other one for production features.
If both widgets are null, we will show the endpoint and appId text fields.

Pre-launch Checklist (For PR creator)

As a creator of this PR:

• ✍️ I have included clickup id and package/app_name in the PR title.
• 👁️ I have gone through the code and removed any temporary changes (commented lines, prints, debug statements etc.).
• ⚒️ I have fixed any errors/warnings shown by the analyzer/linter.
• 📝 I have added documentation, comments and logging wherever required.
• 🧪 I have added necessary tests for these changes.
• 🔎 I have ensured all existing tests are passing.

Reviewers

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• ✴️ This PR follows the standard PR template.
• 🪩 The information in this PR properly reflects the code changes.
• 🧪 All the necessary tests for this PR's are passing.

Pre-launch Checklist (For QA)

• 👌 It passes the acceptance criteria.

Pre-launch Checklist (For Maintainer)

• [MAINTAINER_NAME] I make sure this PR fulfills its purpose.