Upgrade to Blacklight 8 and Bootstrap 5

[granta03]

Blacklight 7 is becoming more and more outdated, as Blacklight 9 released recently. We will need to upgrade the blacklight gem and any other gem dependencies required for it.

Some guides for migrating:

https://github.com/projectblacklight/blacklight/wiki/Upgrading-to-Blacklight-8
https://github.com/projectblacklight/blacklight/wiki/Upgrading-to-Blacklight-9

[granta03]

Upgrading to 9 is not possible at this time due to a dependency in the blacklight_oai_provider gem. 8 is possible. Bootstrap will also need to be upgraded to version 5.