refactor(cli): simplify and clean up new command option mapping

[Nika-HISK]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

The new command contains repetitive logic for parsing and mapping CLI options.
Language validation and CLI option transformation are done manually and imperatively.

Issue Number: N/A

What is the new behavior?

• Introduces a centralized language normalization map (typescript -> ts, etc.)
• Dynamically maps CLI flags into internal Input[] format
• Reduces repetitive .push() calls
• Improves readability and future extensibility

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

This change does not affect CLI output or logic, only simplifies internal structure of the new command handler.