misc(moonbit): language update for MoonBit

[peter-jerry-ye]

This PR contains changes to keep update with the programming language MoonBit

• It updates some visibility decoration based on the grammar change
• It switches the type Bytes to FixedArray[Byte] as per language design of having Bytes as an immutable data structure. In the future, for imported functions, more variants may be provided to avoid transformation between data types.
• It uses Float for all f32 occurrences.

It also adds two new options

• User can choose not to generate moon.mod.json, which may be useful if it were inside a larger project, or
• User can choose the generated project name / package name instead of using the one defined in the WIT file.