use simplyblock v2 API to contact storage backend

[boddumanohar]

At the moment, we contact Simplyblock storage API at 2 places:

1. To update IOPS limits directly by contacting backend. Because Simplyblock CSI driver doesn't support MODIFY_VOLUME feature yet. This WIP in implement controller Modify Volume simplyblock-csi#243
2. To get LVOL stats

As a part of this PR, I've extracted simplyblock related code to a common utils. and used it at both the above 2 places

The format of the response returned by IO Stats API is:

curl -X 'GET' \
  'http://192.168.10.146/api/v2/clusters/cdd0c140-5536-428f-bf4e-3cbf3efe1e9b/storage-pools/48f21f20-5d1d-4d6f-8ce3-9a4359f38bd8/volumes/c7bd1515-3594-4fd4-87c9-bca9bf14b75b/iostats' \
  -H 'accept: application/json' \
  -H 'Authorization: Bearer Z1rgRiHggESpKZICZAwJ'

[
  {
    "date": 1763755862,
    "read_bytes": 7094272,
    "read_bytes_ps": 1638,
    "read_io_ps": 0,
    "read_latency_ps": 1193979,
    "write_bytes": 68857856,
    "write_bytes_ps": 0,
    "write_io_ps": 0,
    "write_latency_ps": 0,
    "connected_clients": 0,
    "size_total": 1073741824,
    "size_prov": 0,
    "size_used": 201326592,
    "size_free": 872415232,
    "size_util": 18,
    "size_prov_util": 0,
    "read_latency_ticks": 7414907680,
    "record_duration": 2,
    "record_end_time": 0,
    "record_start_time": 0,
    "unmap_bytes": 1073745920,
    "unmap_bytes_ps": 0,
    "unmap_io": 2,
    "unmap_io_ps": 0,
    "unmap_latency_ps": 0,
    "unmap_latency_ticks": 106612,
    "write_latency_ticks": 159941744542
  }
]

[mxsrc]

I like this, but ideally we make the API module more self-contained, s.t. we can more easily replace it with a generated one. I think a good way would be to export a class that offers the pool() and volume_iostats() functions.

[mxsrc]

Thanks, this is much nicer already! I think we should make the SimplyblockApi class a bit more powerful, that would improve usage even more.

[boddumanohar]

The linter failure (helm charts) seems un-related to the changes in the PR

[mxsrc]

Looks good, thanks!