fix: flatten module return function when module default is function

[unformalized]

Description

remote client use shared module like dayjs which export default a function, will get a type error: xxx is not function
flattenModule function return object or not a function when module default export is function

fix issue 537

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[ruleeeer]

It looks like this change was made to keep webpack and rollup's exports of CJS libraries consistent. Would such a change cause other lib problems?

[bustEXZ]

The problem is that at the assembly level, shared does not know what is ultimately there, and if there is a function in the module, it does not change dayjs() to dayjs.default(), the same with clsx