refactor: Create Printer object to manage output

[TerryHowe]

What this PR does / why we need it:

Create a printer object to manage output

[codecov]

Codecov Report

Attention: Patch coverage is 93.10345% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 82.02%. Comparing base (f1d319f) to head (4417131).
Report is 19 commits behind head on main.

❗ Current head 4417131 differs from pull request most recent head 1db763f. Consider uploading reports for the commit 1db763f to get more accurate results

Files	Patch %	Lines
cmd/oras/root/login.go	66.66%	1 Missing and 2 partials ⚠️
cmd/oras/root/discover.go	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1292      +/-   ##
==========================================
+ Coverage   81.94%   82.02%   +0.07%     
==========================================
  Files          83       83              
  Lines        4005     4022      +17     
==========================================
+ Hits         3282     3299      +17     
  Misses        500      500              
  Partials      223      223              

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[qweeah]

@TerryHowe Is this blocking your implementation of ORAS Golang scripting? IMHO this output should be classified to metadata output and it's better to user metadata push handler rather than new printer:

_, displayMetadata := display.NewPushHandler("", nil, opts.Verbose) // avoiding formatting and TTY output
displayMetadata.OnCopied(&opts.Target)

[TerryHowe]

What I'm trying to develop here is a layer similar to logrus that doesn't know what is is printing, it just knows how to print. To me at least, ideally the format code would be a layer on top of that.

[qweeah]

Gotcha. Any good idea to inject the writer in? The writer might come from STDOUT or cobra command output.

[qweeah]

@TerryHowe I added a new Printer interface to display package to unify the output into STDOUT.

oras/cmd/oras/internal/display/metadata/view/printer.go

Lines 33 to 40 in 61e0241

	// Printer prints.
	type Printer interface {
	Printf(format string, a ...any) (n int, err error)
	Println(a ...any) (n int, err error)
	PrintJSON(object any) error
	ParseAndWrite(object any, templateStr string) error
	Outputable
	}

It provides PrintXXX to wrap fmt.FprintXXX utilities, also provides PrintJSON and ParseAndWrite for formatted output

To reflect your changes in #1288, cobra.Command.OutOrStdout can be injected via below interface

oras/cmd/oras/internal/display/metadata/view/printer.go

Lines 27 to 31 in 61e0241

	// Outputable interface is used to reset output of the handler.
	type Outputable interface {
	// WithOutput resets output of the handler.
	WithOutput(out io.Writer)
	}

Please help you help review related changes in #1310 and let me know your comment on this design, thanks.

[qweeah]

@TerryHowe I have added another solution in #1314, please let me know if it meets your expectation.