[shaktimaan00]

Closes #7904

Change Description

Background

lakectl has template based helpers for writing to stdout and stderr, but they
live in cmd/lakectl/cmd/common_helpers.go and cannot be imported by the
lakefs server binary. As a result, lakefs grew its own small set of print
helpers (printMsgAndExit, printInfo, printNonFatalError, added for the
flare command). This moves the shared implementation into a package that both
binaries import.

New Feature

New package pkg/cmdutils/output.go (next to the existing cmdutils
progress/validation/coalesce helpers) with the output utilities:

• ColoredText, Table, Pagination and the template functions behind
  red/yellow/green/blue/bold/underline, date, ljust, json,
  table, paginate, lower, human_bytes and join.
• WriteTo, Write, Warning, Die, DieFmt, DieErr, PrintTable, plus
  the DeathMessage, DeathMessageWithFields, WarnMessage, InfoMessage and
  ErrorMessage templates.
• DisableColors/IsTerminal, so the "no colors, no terminal only niceties"
  switch applies to every consumer.
• InfoFmt and NonFatalErrorFmt, replacing lakefs' printInfo and
  printNonFatalError.

cmd/lakectl/cmd/common_helpers.go keeps thin wrappers with its existing
signatures (WriteTo(tpl, data, w), Colored, Table/Pagination/ColoredText
type aliases, ...) so none of the ~135 lakectl command files had to change.
cmd/lakefs/cmd/common_helpers.go is deleted and gc.go/flare.go call
cmdutils directly.

Testing Details

• go build ./...
• go vet ./cmd/lakectl/... ./cmd/lakefs/... ./pkg/cmdutils/...
• go test ./cmd/lakectl/cmd/... — passes, including TestColors, which
  exercises the moved WriteTo template functions through the wrapper.

Breaking Change?

No API or client change. One user visible difference: errors from the lakefs
binary now print through the shared DeathMessage template, i.e.

<error in red>
Error executing command.

instead of Error: <error>. Info/Error non-fatal messages and the flare
warnings keep their previous meaning, now covering both binaries.

[shaktimaan00]

Closing this in favour of #10610, which I opened a minute later — same issue, same approach, so having both open just splits the review. Sorry for the duplicate.

The two differences, so the choice is clear if you would rather have this one:

• Share the CLI output utilities between lakectl and lakefs #10610 keeps lakefs output byte-for-byte identical (printInfo/printNonFatalError/printMsgAndExit render through the shared engine with equivalent templates, verified by comparing old and new implementations). This PR instead routes lakefs errors through DeathMessage, which changes what users see (Error: <msg> -> <msg in red> + Error executing command.).
• Share the CLI output utilities between lakectl and lakefs #10610 leaves Die, Warning and PrintTable in cmd/lakectl/cmd, so the shared package does not call os.Exit or write to os.Stdout on a caller's behalf.
• Share the CLI output utilities between lakectl and lakefs #10610 adds tests for the non-interactive table/pagination paths and moves TestColors next to the renderer.

Both branches build and their tests pass; nothing in this branch is needed by #10610.