Improve error message for missing access attribute in intercept-url

[chanani]

Description

Improves error handling when <intercept-url> elements are missing the required access attribute.

Changes

• Add validation in AuthorizationFilterParser to check for missing or empty access attribute
• Add validation in FilterInvocationSecurityMetadataSourceParser for legacy mode
• Add comprehensive test coverage for both authorization modes

Before

Missing or empty access attributes were silently accepted, causing cryptic errors during bean initialization:

java.lang.IllegalArgumentException: Cannot invoke "String.isEmpty()" because "access" is null

After

Clear error message at configuration parsing time:

Configuration problem: access attribute cannot be empty or null

Testing

• Added test cases for missing access attribute
• Added test cases for empty access attribute
• Added test cases for valid access attribute
• Tested both AuthorizationManager and legacy AccessDecisionManager modes

Fixes gh-18503

[chanani]

Hi @rwinch ! 👋

I've submitted this PR to address issue #18503. This adds validation for missing or empty access attributes in <intercept-url> elements with clear error messages.

Would appreciate your review when you have time. Thank you!