[PM-29304] feat: Add custom field autofill support with strict URI matching

[gryphon2411]

Implements support for autofilling custom fields defined in vault items.

• Updates parsing logic to identify generic inputs as 'Custom' candidates.
• Updates filling logic to match custom fields by name/label against view hints/IDs.
• Enforces strict URI matching for custom fields as a security mitigation.
• Fixes regression where generic inputs were ignored for username autofill.

Verification

I have verified this functionality using the Android Emulator (API 35) and the standardDebug build.

Test Case: Timewatch.co.il

1. URL: https://c.timewatch.co.il/punch/punch.php
2. Vault Item:
   • URI: https://c.timewatch.co.il (Strict match)
   • Username: 12345 (Employee Number)
   • Password: ******
   • Custom Field: Name: company, Value: comp123
3. Result:
   • Tapping "Company Number" autofills comp123.
   • Tapping "Employee Number" autofills 12345.
   • Tapping "Password" autofills ******.

Automated Tests:

• Added FilledDataBuilderCustomFieldTest: Verifies strict matching and field mapping.
• Added AutofillParserRegressionTests: Verifies generic input promotion to Username.

Context

Ref: PM-29304 (Internal Ticket)

Addresses community feature requests for Android Custom Field Autofill:

• Community Forum: https://community.bitwarden.com/t/android-please-add-support-for-autofilling-custom-fields-in-the-bitwarden-app/89621
• GitHub Discussion: https://github.com/orgs/bitwarden/discussions/16722

[bitwarden-bot]

Thank you for your contribution! We've added this to our internal tracking system for review.
ID: PM-29304
Link: https://bitwarden.atlassian.net/browse/PM-29304

Details on our contribution process can be found here: https://contributing.bitwarden.com/contributing/pull-requests/community-pr-process.