[FEATURE] Add labels to as input to environment instance

[lechnerc77]

Labels are currently not supported as input from the users.
We must support this feature to enable customers to specify their labels for the environment instances as they can do it via the BTP CLI:

• Labels are defined as optional input parameters of resource
• Labels are considered in ``CREATE, UPDATE` and `IMPORT` operations
• Testcases are adjusted accordingly

[lechnerc77]

• Supported via Cockpit in feature set b (link)
• Currently not supported by BTP CLI (see https://help.sap.com/docs/btp/btp-cli-command-reference/btp-create-accounts-environment-instance)
• For SAP Internals only: Jira Ticket

SAP internal clarification ongoing.