add more tests, some tweaks for error messages

[matyalatte]

I added more unit tests for future updates, and fixed nits.

• Fixed a bug where an error message for unknown codepages did not have line and column.
• static_text now does not throw errors for duplicated IDs.
• An error message for unknown component types is now prioritized over other component errors.
• Fixed a crash when noex::vector threw the out of bounds error.
  (Tuw does not throw the out of bounds error tho.)

Note

This patch just changes some JSON error messages. There is nothing you should inform to users.