Add --format flag support to rt commands

[ehl-jf]

Summary

Adds --format flag support to several rt commands so their output can be machine-consumed (JSON) and, where useful, rendered as a summary table. Behavior without --format is unchanged.

Commands now accepting --format:

Command	Accepted values
rt permission-target-create (ptc)	json
rt permission-target-update (ptu)	json
rt users-create (uc)	json
rt transfer-config	json
rt transfer-config-merge	json, table
rt transfer-files	json, table

Implementation notes:

• permission-target-create / permission-target-update: switched from TemplateConsumer flag set to dedicated PermissionTargetCreate / PermissionTargetUpdate keys so the new --format flag is actually wired in (fix in commit 946c0320).
• For commands whose underlying client layer discards the response body, a synthetic {"status_code":200,"message":"OK"} payload is emitted via cliutils.FormatHTTPResponseJSON on success.
• transfer-config-merge and transfer-files get richer structured output: a transferConfigMergeResult / transferFilesResult struct rendered as either JSON or a tabwriter summary table.
• New flag entries (permission-target-create-format, permission-target-update-format, transfer-config-format, transfer-config-merge-format, transfer-files-format, users-create-format) registered in utils/cliutils/commandsflags.go.

Tests:

• artifactory/cli_test.go: +509 lines covering format parsing, JSON/table rendering, error propagation, and unsupported-format handling for the affected commands.

Dependencies:

• Bumps jfrog-cli-artifactory to 0.8.1-0.20260512080921-ec417dc1b7ee.
• Bumps jfrog-client-go to 1.55.1-0.20260508101905-a17af78a38d7.

Files changed: artifactory/cli.go, artifactory/cli_test.go, utils/cliutils/commandsflags.go, go.mod, go.sum.

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• All tests have passed. If this feature is not already covered by the tests, new tests have been added.
• The pull request is targeting the master branch.
• The code has been validated to compile successfully by running go vet ./....
• The code has been formatted properly using go fmt ./....

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