[TT-13588] Add new field to support configuration of TYK_API_PORT

[komalsukhani]

Description

Added new field in tyk-dashboard chart dashboard.tykApiPort to configure value of TYK_API_PORT.

Related Issue

https://tyktech.atlassian.net/browse/TT-13558
Resolves #355

Motivation and Context

Test Coverage For This Change

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactoring or add test (improvements in base code or adds test coverage to functionality)
• Documentation updates or improvements.

Checklist

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• My change requires a change to the documentation.
  • I have manually updated the README(s)/documentation accordingly.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.