CPLAT-4058 Provide additional --help output and better stderr

[smaifullerton-wk]

• Created an ArgParser with the --backwards-compat flag and passed its usage to runInteractiveCodemod so that it'll be formatted as an additional --help option

• Created _changesRequiredOutput and passed into both phases of codemod, so that if either one fails the user will receive a helpful message.

• Fixed a bug, --help output is being printed twice, one in each phase of codemod. Now it's only the first one.

[aviary-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure
• Verify aviary.yaml coverage of security relevant code

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Questions or Comments? Reach out on Slack: #support-infosec.

[evanweible-wf]

QA +1

• CI passes
• Verified the stderr output for:
  • pub run over_react_codemod:dart2_upgrade -h
  • pub run over_react_codemod:dart2_upgrade --fail-on-changes

@Workiva/release-management-p