feat: Add support for custom microfrontends.json naming (#11022)
### Description
Allowing users to customize the name of their microfrontends file using
a `VC_MICROFRONTENDS_CONFIG_FILE_NAME` environment variable. Only
accepts file names at the root of the package
### Testing Instructions
Added some tests and make sure it works manually.
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Co-authored-by: Anthony Shew <anthonyshew@gmail.com>
