[Vis Colors] Remove hard coded color values from visualization functional tests

[manasvinibs]

We have functional tests for dashboard state and app, which uses legacy seed colors, hard coded RGB and hex values of colors to test the Dashboard visualization functionality. We need to refactor all such tests to use colors from OUI.
Few such examples below -

OpenSearch-Dashboards/test/functional/apps/dashboard/dashboard_state.js

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await PageObjects.visChart.selectNewLegendColorChoice('#F9D9F9');

OpenSearch-Dashboards/test/functional/apps/dashboard/dashboard_state.js

Line 256 in 29d7a4b

if (style.indexOf('rgb(255, 255, 255)') > 0) {

OpenSearch-Dashboards/test/functional/apps/dashboard/dashboard_state.js

Line 281 in 29d7a4b

expect(pieSliceStyle.indexOf('rgb(87, 193, 123)')).to.be.greaterThan(0);

OpenSearch-Dashboards/test/functional/apps/dashboard/dashboard_state.js

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const colorExists = await PageObjects.visChart.doesSelectedLegendColorExist('#57c17b');