fix(elasticloadbalancingv2): crossZoneEnabled does not support false for ALB

[pahud]

Issue # (if applicable)

Closes #29866

Reason for this change

crossZoneEnabled is not well handled when it's false with ALB. Because:

1. When the L2 prop is set false, it will not pass down to the L1 and won't throw any error as ALB does not support being disabled. It just silently ignore it.
2. When the prop is false for NLB, the L1 attribute will be undefined, which is having the same result but it should be explicitly set as false in L1.

This PR covers the following cases:

1. When crossZoneEnabled is true, load_balancing.cross_zone.enabled should be true.
2. When crossZoneEnabled is false, load_balancing.cross_zone.enabled should be false, rather than undefined.
3. When crossZoneEnabled is false with ALB, cdk throws an error because ALB does not support disabling it per doc description.
4. NLB supports either true or false.
5. This prop can be undefined for ALB or NLB.
6. Improve the doc string for the crossZoneEnabled prop.

Description of changes

Description of how you validated changes

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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

[GavinZZ]

LGTM

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: d8936b9
• Result: SUCCEEDED
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