pallet-asset: Added new test cases for invalid asset value Fixes #372

[ritankarsaha]

This PR fixes the issue #372

Implementation Approach

1. Analyzed existing test cases (particularly asset_create_should_succeed) as referenced in the issue
2. Identified all functions that could return InvalidAssetValue error
3. Wrote test cases for efficiency while maintaining comprehensive coverage
4. Implemented test validating:
   • Regular asset creation with invalid value
   • VC asset creation with invalid quantity

Testing

• All new tests can be executed using cargo test -p pallet-asset
• Test cases validate proper error handling

Below is the attached screenshot of the test case passing in the local environment:-

[ritankarsaha]

@vatsa287 is this implementation correct or does this PR require any more changes??

[vatsa287]

@ritankarsaha Please go through the review comments on this PR #520. Make similar changes here.