refactor(cli): replace log with logrus for structured logging. Fixes #2308

[suzuki-shunsuke]

This pull request just replaces the standard package log to logrus for structured logging.

#2308

All log package is replaced.

$ ag '"log"'   
cmd/argo/commands/submit.go
97:	command.Flags().BoolVar(&cliSubmitOpts.log, "log", false, "log the workflow until it completes")

cmd/argo/commands/retry.go
79:	command.Flags().BoolVar(&cliSubmitOpts.log, "log", false, "log the workflow until it completes")

workflow/common/util.go
94:		SubResource("log").

pkg/apiclient/workflow/workflow.pb.gw.go
1769:	pattern_WorkflowService_PodLogs_0 = runtime.MustPattern(runtime.NewPattern(1, []int{2, 0, 2, 1, 2, 2, 1, 0, 4, 1, 5, 3, 1, 0, 4, 1, 5, 4, 1, 0, 4, 1, 5, 5, 2, 6}, []string{"api", "v1", "workflows", "namespace", "name", "podName", "log"}, "", runtime.AssumeColonVerbOpt(true)))

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I've signed the CLA.
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My builds are green. Try syncing with master if they are not.
• My organization is added to USERS.md.

[alexec]

I think "structured logging" might mean something different to you. For me it essentially means using log.Fields{} so that logs can be easily queried in Splunk.

[alexec]

Looks great so far!

        --- FAIL: TestCLIWithServerSuite/TestTemplate/Get (0.06s)
            cli_test.go:667: 
                	Error Trace:	cli_test.go:667
                	            				given.go:179
                	            				cli_test.go:665
                	            				suite.go:77
                	Error:      	"time=\"2020-07-10T14:46:47Z\" level=fatal msg=\"rpc error: code = NotFound desc = workflowtemplates.argoproj.io \\\"not-found\\\" not found\"\n" does not contain "\"not-found\" not found"

There are failing tests that need to be fixed.

[suzuki-shunsuke]

Thank you for your review.
I found my misunderstanding.

The code changed in this pull request is for CLI tool, but #2808 intends to change the logging of the server side.
logrus is already used at the server side, but #2808 means that the fields are insufficient.