Refactor/Reorganize object/acl

[carpawell]

Alternative to #1095 solution of the #596.

Since it was decided to keep logic that works with requests in the repo (and not move it to SDK) it is impossible to remove v2 package in object/acl service since something has to work with v2 requests anyway (implement interface in object pipeline in other words). So that PR reorganizes the structure of that directory to be similar to other packages in service/object: there are v2 packages in acl and acl/eacl dirs now. They parse all v2-versioned structs into neofs-sdk-go abstractions and pass them to the corresponding acl/eacl packages. v2 packages are the only packages that do import neofs-api-go library. eacl and acl provide public functions that only accepts sdk structures.

Valid only after nspcc-dev/neofs-sdk-go#128 and rebasing.

[codecov]

Codecov Report

Merging #1111 (e8a62ff) into master (7ccd162) will decrease coverage by 0.11%.
The diff coverage is 7.36%.

❗ Current head e8a62ff differs from pull request most recent head bed2e83. Consider uploading reports for the commit bed2e83 to get more accurate results

@@            Coverage Diff             @@
##           master    #1111      +/-   ##
==========================================
- Coverage   35.64%   35.52%   -0.12%     
==========================================
  Files         284      288       +4     
  Lines       18055    18008      -47     
==========================================
- Hits         6435     6397      -38     
+ Misses      11129    11126       -3     
+ Partials      491      485       -6     

Impacted Files	Coverage Δ
pkg/services/object/acl/basic_helper.go	34.78% <ø> (ø)
pkg/services/object/acl/eacl/v2/localstore.go	0.00% <0.00%> (ø)
pkg/services/object/acl/eacl/v2/opts.go	36.84% <0.00%> (ø)
pkg/services/object/acl/v2/classifier.go	0.00% <0.00%> (ø)
pkg/services/object/acl/v2/errors.go	0.00% <0.00%> (ø)
pkg/services/object/acl/v2/opts.go	0.00% <0.00%> (ø)
pkg/services/object/acl/v2/request.go	0.00% <0.00%> (ø)
pkg/services/object/acl/v2/service.go	0.00% <0.00%> (ø)
pkg/services/object/acl/v2/util.go	7.54% <7.54%> (ø)
pkg/services/object/acl/eacl/v2/headers.go	39.79% <26.66%> (-0.41%)	⬇️
... and 33 more

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