[Consideration] Guarantee of idempotency when applying transform plugins (after v0.4.0)

[yukihirop]

Summary

Generally, when applying a transform plug-in system, there should be idempotency that the same result can be obtained no matter how many times it is executed.

However, since it is not, I will correct it so that it becomes idempotent.

[yukihirop]

Abolish routes:oas:plugin command so that the plugin is applied and the file is output when routes:oas:dist command is executed

rename routes:oas:dist to routes:oas:build