[charts/gateway] - Adding provision to add additional system properties

[snagarjunas]

Description of the change

Adding provision to add additional system properties via name value pairs

Benefits

Users can now add additional system properties. These new properties get added under existing system properties

Drawbacks

Applicable issues

• fixes #

Additional information

Checklist

• [] Chart version bumped in Chart.yaml according to semver.
• [] Variables are documented in the README.md
• [] Title of the PR starts with chart name (e.g. [charts/gateway])
• [] If the chart contains a values-production.yaml apart from values.yaml, ensure that you implement the changes in both files