Upgrade BookReaderAuth.php and borrow.py make_ia_token to use stronger hash

### Problem

In https://github.com/internetarchive/openlibrary/blob/0dfc2fafc096823dc1ed6268e30bdbca65ce3240/openlibrary/plugins/upstream/borrow.py#L773-L785 we make a call to BookReaderAuth.php and pass in an iaAuthToken. We may want to extend BookReaderAuth.php to also support iaStrongAuthToken which is a new field we can use to move from md5 to a stronger hash while not breaking any other code path that is using / relying on iaAuthToken.

### Reproducing the bug

1. Go to ...
2. Do ...

* Expected behavior:
* Actual behavior:

### Context

- Browser (Chrome, Safari, Firefox, etc):
- OS (Windows, Mac, etc):
- Logged in (Y/N):
- Environment (prod, dev, local): prod

### Breakdown

#### Requirements Checklist
* [ ]

#### Related files

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#### Stakeholders

* cc: @cdrini

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