refactor: transtition to spdk client

[artek-koltun]

spdk rolled out its own client, and we can start transition to that client from our custom solution

This PR is a first step of the integration.

An adapter struct between the new and old APIs was created in order to address the following obstacles:

• Awkward response unmarshaling in the new client (SPDK team is working on that).
• The new error formats are affecting a lot of tests. The adapter convert the new format to the old one. It enables a gradual transition. The tests will be reworked to the new errors, eliminating transformations in the adapter one by one.

Opens:

• How to resist against error changes in spdk, so that we don't need to rework tons of tests?
  • Probability is low that the error will change frequently in SPDK. Do we really need to focus on that issue, then?
  • Use predefined set of errors and return them.
  • Check for keywords in an error message, not exact matching.
  • Check that error was received and disregard the content of the string.
  • ...
• tracing is on our side or try to push an interface to spdk client (it knows all attributes) for tracing, so anyone could inject its own tracing functionality

[codecov]

Codecov Report

Attention: 66 lines in your changes are missing coverage. Please review.

Comparison is base (55e38cf) 74.77% compared to head (9d0d950) 74.19%.
Report is 6 commits behind head on main.

Files	Patch %	Lines
pkg/utils/server.go	0.00%	54 Missing ⚠️
pkg/spdk/adapter.go	86.04%	6 Missing ⚠️
pkg/backend/backend.go	50.00%	1 Missing and 1 partial ⚠️
pkg/frontend/frontend.go	71.42%	1 Missing and 1 partial ⚠️
pkg/middleend/middleend.go	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #875      +/-   ##
==========================================
- Coverage   74.77%   74.19%   -0.59%     
==========================================
  Files          40       41       +1     
  Lines        3699     3778      +79     
==========================================
+ Hits         2766     2803      +37     
- Misses        845      887      +42     
  Partials       88       88              

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