Build: Add a retry mechanism for exports file generation

[ndelangen]

Issue:
On some CI runs, and sometimes locally as well, (@shilman reported this stack trace to me), we get this:

    ✖  nx run @storybook/manager:prep
       > /Users/shilman/projects/storybookjs/storybook/scripts/node_modules/.bin/ts-node ./scripts/generate-exports-file.ts
       An error occurred while executing: `/Users/shilman/projects/storybookjs/storybook/scripts/node_modules/.bin/ts-node ./scripts/generate-exports-file.ts`
       undefined

       Error: Command failed with exit code 1: /Users/shilman/projects/storybookjs/storybook/scripts/node_modules/.bin/ts-node ./scripts/generate-exports-file.ts
       An error occurred while executing: `yarn lint:js:cmd --fix /Users/shilman/projects/storybookjs/storybook/code/ui/manager/src/globals/exports.ts`
       Error: Command failed with exit code 1: yarn lint:js:cmd --fix /Users/shilman/projects/storybookjs/storybook/code/ui/manager/src/globals/exports.ts

       /Users/shilman/projects/storybookjs/storybook/code/ui/manager/src/globals/exports.ts
         0:0  error  Parsing error: Debug Failure. False expression: /users/shilman/projects/storybookjs/storybook/code/node_modules/@storybook/addon-actions/dist/manager.d.ts linked to nonexistent file /Users/shilman/projects/storybookjs/storybook/code/addons/actions/dist/manager.d.ts

What I did

I added a retry mechanism, in the hope that after 6 attempts it should have worked.

This is under the assumption that there's some race condition going on.
I tried a few things to reproduce locally, but was not successful at doing so.

Therefore I resorted to adding a retry mechanism, hoping the problem stays away now.

[ndelangen]

self merging @shilman

[IanVS]

I think this probably isn't needed if #20021 is merged. @ndelangen maybe you can take a look or explain why this retry is needed vs the simpler approach in that PR?