feat: add batch cacher

[cre8ivejp]

Part of #405 and #820

I will add the cronjob in another PR.

Things done

• Added feature flag cacher
• Added segment user cacher
• Added environment API key cacher
• Added experiment cacher
• Added auto ops rules cacher
• Added unit tests

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This pull request primarily extends the functionality of the batchService struct in pkg/batch/api/api.go by adding new cache jobs for feature flags, segment users, API keys, experiments, and autoOps rules. Additionally, the testing suite in pkg/batch/api/api_test.go has been updated to include tests for these new jobs and to make use of parallel testing.

Here are the most important changes:

New cache jobs in batchService:

• type batchService struct {: Added featureFlagCacher, segmentUserCacher, apiKeyCacher, experimentCacher, and autoOpsRulesCacher as new job fields in the batchService struct.
• func NewBatchService(: Updated the function parameters and the returned batchService to include the new jobs. [1] [2]
• func (s *batchService) ExecuteBatchJob(: Extended the switch-case statement to handle the execution of the new jobs.

Updates to the testing suite:

• pkg/batch/api/api_test.go: Added new imports for the mock clients needed for the new tests. [1] [2]
• type setupMockFunc func(: Extended the setupMockFunc type to include the new mock clients. [1] [2]
• func TestExperimentStatusUpdater(t *testing.T) { and other test functions: Updated the setupMock function calls to include the new mock clients and added the t.Parallel() directive to enable parallel testing. [1] [2] [3] [4] [5] [6] [7]
• func TestFeatureFlagCacher(t *testing.T) { and other new test functions: Added new test functions for the new jobs in batchService.
• func newBatchService(t *testing.T,: Updated the function to create a new batchService for testing to include the new mock clients.