fix: not mangle export with destructuring

[ahabhgk]

fix #18013

What kind of change does this PR introduce?

fix not mangle the export when destructuring module's export.
when destructuring a module: let { export1 } = m, can't mangle the export1.
but when destructuring a module's export: let { a } = m.export1, can mangle the export1

Did you add tests for your changes?

added

Does this PR introduce a breaking change?

no

What needs to be documented once your changes are merged?

none

[webpack-bot]

For maintainers only:

• This needs to be documented (issue in webpack/webpack.js.org will be filed when merged)
• This needs to be backported to webpack 4 (issue will be created when merged)

[alexander-akait]

Thank you