feat(elb): add new check `elb_cross_zone_load_balancing_enabled`

[puchy22]

Context

This PR introduces a new check for ensuring that Cross-Zone Load Balancing is enabled for Classic Load Balancers (CLBs) in AWS environments. Cross-Zone Load Balancing is essential for maintaining fault tolerance and evenly distributing traffic across all registered instances in different Availability Zones (AZs). Without this feature, traffic might be unevenly distributed, leading to performance degradation and potential application downtime.

Description

• [x] Modify service to add CrossZone attribute to ELB
• [x] Test service changes
• [x] Add check logic
• [x] Add unit testing for the check

Checklist

• Are there new checks included in this PR? Yes
  • If so, do we need to update permissions for the provider? No.
• [x] Review if the code is being covered by tests.
• [x] Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.15%. Comparing base (a557d62) to head (078ab6e). Report is 26 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4818 +/- ## ========================================== + Coverage 89.05% 89.15% +0.09% ========================================== Files 926 930 +4 Lines 28363 28484 +121 ========================================== + Hits 25258 25394 +136 + Misses 3105 3090 -15 ```

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