Reduce time complexity by modifying the data structure

[hlts2]

WHAT

Modified the data structure to reduce the time complexity of the access mode existence check for volumes during RPC calls. This enables existence checks to be performed in O(1) time.

WHY

A loop was used each time to check if there was a matching access mode for Volume. Currently, the loop only runs twice, so it's not an issue, but optimizing to O(1) check is better in case the number of access modes for Volume increases in the future.

Below is a list of possible options.

- csi.pb.go
  - VolumeCapability_AccessMode_SINGLE_NODE_WRITER
  - VolumeCapability_AccessMode_SINGLE_NODE_READER_ONLY
  - VolumeCapability_AccessMode_MULTI_NODE_READER_ONLY
  - VolumeCapability_AccessMode_MULTI_NODE_SINGLE_WRITER
  - VolumeCapability_AccessMode_MULTI_NODE_MULTI_WRITER 
  - VolumeCapability_AccessMode_SINGLE_NODE_SINGLE_WRITER
  - VolumeCapability_AccessMode_SINGLE_NODE_MULTI_WRITER

FYI

This PR includes only changes to the data structure, so no logic modifications have been made 🙏
Additionally, the supportedAccessModes variable was not used anywhere outside of pkg/driver/controller_server.go, so there were no changes made in other areas.

❯ rg supportedAccessModes
pkg/driver/controller_server.go
22:var supportedAccessModes = map[csi.VolumeCapability_AccessMode_Mode]struct{}{
43:		if _, ok := supportedAccessModes[cap.GetAccessMode().GetMode()]; !ok {
469:		if _, ok := supportedAccessModes[cap.GetAccessMode().GetMode()]; ok {

The following is the test result.

❯ go test -v ./controller_server_test.go
=== RUN   TestCreateVolume
=== RUN   TestCreateVolume/Create_a_default_size_volume
{"level":"info","api_url":"https://civo-api.example.com","region":"TEST1","namespace":"default","cluster_id":"12345678","socketFilename":"unix:///var/lib/kubelet/plugins/civo-csi/csi.sock","user_agent":"civo-csi","time":"2024-11-07T03:07:29+09:00","message":"Created a new driver"}
=== RUN   TestCreateVolume/Disallow_block_volumes
=== RUN   TestCreateVolume/Create_a_specified_size_volume
=== RUN   TestCreateVolume/Don't_create_if_the_volume_already_exists_and_just_return_it
--- PASS: TestCreateVolume (0.00s)
    --- PASS: TestCreateVolume/Create_a_default_size_volume (0.00s)
    --- PASS: TestCreateVolume/Disallow_block_volumes (0.00s)
    --- PASS: TestCreateVolume/Create_a_specified_size_volume (0.00s)
    --- PASS: TestCreateVolume/Don't_create_if_the_volume_already_exists_and_just_return_it (0.00s)
=== RUN   TestDeleteVolume
=== RUN   TestDeleteVolume/Delete_a_volume
--- PASS: TestDeleteVolume (0.00s)
    --- PASS: TestDeleteVolume/Delete_a_volume (0.00s)
=== RUN   TestControllerPublishVolume
=== RUN   TestControllerPublishVolume/Publish_a_volume
--- PASS: TestControllerPublishVolume (5.00s)
    --- PASS: TestControllerPublishVolume/Publish_a_volume (5.00s)
=== RUN   TestControllerUnpublishVolume
=== RUN   TestControllerUnpublishVolume/Unpublish_a_volume_if_attached_to_the_correct_node
=== RUN   TestControllerUnpublishVolume/Doesn't_unpublish_a_volume_if_attached_to_a_different_node
--- PASS: TestControllerUnpublishVolume (5.00s)
    --- PASS: TestControllerUnpublishVolume/Unpublish_a_volume_if_attached_to_the_correct_node (5.00s)
    --- PASS: TestControllerUnpublishVolume/Doesn't_unpublish_a_volume_if_attached_to_a_different_node (0.00s)
=== RUN   TestListVolumes
=== RUN   TestListVolumes/Lists_available_existing_volumes
--- PASS: TestListVolumes (0.00s)
    --- PASS: TestListVolumes/Lists_available_existing_volumes (0.00s)
=== RUN   TestGetCapacity
=== RUN   TestGetCapacity/Has_available_capacity_from_usage_and_limit
=== RUN   TestGetCapacity/Has_no_capacity_from_usage_and_limit
=== RUN   TestGetCapacity/Has_no_capacity_from_volume_count_limit
--- PASS: TestGetCapacity (0.00s)
    --- PASS: TestGetCapacity/Has_available_capacity_from_usage_and_limit (0.00s)
    --- PASS: TestGetCapacity/Has_no_capacity_from_usage_and_limit (0.00s)
    --- PASS: TestGetCapacity/Has_no_capacity_from_volume_count_limit (0.00s)
PASS
ok  	command-line-arguments	10.012s

[rytswd]

Thanks! Small and iterative changes which we all love 😆

[hlts2]

@Praveen005 @rytswd
Thank you for reviewing it!
I will merge this PR 🚀