chore: use golangci lint

[kranurag7]

What this PR does / why we need it:
The following are the places that's giving some errors as of now according to the linter.

output of running golangci locally

$ golangci-lint run
cmd/oras/root/attach.go:94:22: Error return value of `cmd.MarkFlagRequired` is not checked (errcheck)
        cmd.MarkFlagRequired("artifact-type")
                            ^
cmd/oras/root/discover.go:191:13: Error return value is not checked (errcheck)
                        printJSON(ref)
                                 ^
cmd/oras/internal/display/print.go:119:9: Error return value is not checked (errcheck)
                        Print("Tagging", ref)
                             ^
cmd/oras/internal/display/print.go:139:9: Error return value is not checked (errcheck)
                        Print("Tagging", ref)
                             ^
cmd/oras/internal/option/packer_test.go:73:14: Error return value of `os.WriteFile` is not checked (errcheck)
        os.WriteFile(testFile, []byte(testContent), fs.ModePerm)
                    ^
cmd/oras/internal/option/remote.go:276:30: Error return value of `repo.SetReferrersCapability` is not checked (errcheck)
                repo.SetReferrersCapability(*opts.distributionSpec.referrersAPI)
                                           ^
cmd/oras/internal/option/remote_test.go:54:29: Error return value of `(*encoding/json.Encoder).Encode` is not checked (errcheck)
                        json.NewEncoder(w).Encode(testTagList)
                                                 ^
cmd/oras/internal/option/remote_test.go:236:28: Error return value of `(*encoding/json.Encoder).Encode` is not checked (errcheck)
                json.NewEncoder(w).Encode(testTagList)
                                         ^
internal/cache/target_test.go:180:12: Error return value of `w.Write` is not checked (errcheck)
                                w.Write(blob)
                                       ^
internal/graph/graph_test.go:142:14: Error return value of `memory.Push` is not checked (errcheck)
                memory.Push(ctx, descs[i], bytes.NewReader(blobs[i]))
                           ^
internal/graph/graph_test.go:258:14: Error return value of `memory.Push` is not checked (errcheck)
                memory.Push(ctx, descs[i], bytes.NewReader(blobs[i]))
                           ^
internal/graph/graph_test.go:356:14: Error return value of `memory.Push` is not checked (errcheck)
                memory.Push(ctx, descs[i], bytes.NewReader(blobs[i]))

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #981

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?

[codecov-commenter]

Codecov Report

Merging #986 (cba6d7a) into main (bf33bb7) will not change coverage.
The diff coverage is n/a.

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@@           Coverage Diff           @@
##             main     #986   +/-   ##
=======================================
  Coverage   81.26%   81.26%           
=======================================
  Files          53       53           
  Lines        2776     2776           
=======================================
  Hits         2256     2256           
  Misses        352      352           
  Partials      168      168           

[qweeah]

Suggested to align with other actions.

Also this PR requires fixing of all detected issues otherwise the PR check will fail. @kranurag7 Do you want to do the fixing? If not have time I can add another PR to fix all the lint issues found.

[qweeah]

@kranurag7 Can you add signoff as is suggested in https://github.com/oras-project/oras/pull/986/checks?check_run_id=14956872091:

• In your local branch, run: git rebase HEAD~3 --signoff
• Force push your changes to overwrite the branch: git push --force-with-lease origin golangci

[TerryHowe]

I just rebased, so you are going to have to git pull and take care of DCO

[TerryHowe]

/lgtm

[qweeah]

LGTM