fix(sandpack): Rewrite import.meta to $csb__import_meta

[DeMoorJasper]

What kind of change does this PR introduce?

Before this PR we didn't touch import.meta which resulted in errors as import.meta is only allowed in ESModules.

What is the current behavior?

We don't do anything with import.meta resulting in errors.

What is the new behavior?

Now sandpack replaces import.meta with $csb__import_meta which we insert as a module-scoped variable if import.meta is used.

What steps did you take to test this? This is required before we can merge, make sure to test the flow you've updated.

Wrote some basic unit tests and tried out this failing sandbox https://codesandbox.io/s/quizzical-cerf-2ph7r?file=/src/index.tsx

Closes CSB-858

[linear]

CSB-858 `import.meta` isn't currently polyfilled

We need to polyfill import.meta.url to get Framer's esmodules to work, this is also a great feature for us in general.

These should be transpiled away to something like $csb_import_meta which we can define at the top of each file

[lbogdan]

Build for latest commit 578c306 is at https://pr6031.build.csb.dev/s/new.

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