fix: [CHK-4715] - opex dashboard generation

[pietro-tota]

List of Changes

Fix opex generation workflow:

• move env files to root .opex folder
• remove unused uat folder
• use matrix approach, as a predisposition to handling more envs

Motivation and Context

Those modifications are needed in order to properly generate opex dashboard based on service openapi

How Has This Been Tested?

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 not work as
  expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[github-actions]

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud