DACCESS-529 - Use rsolr instead of HTTPClient in BrowseController

[chrisrlc]

https://culibrary.atlassian.net/browse/DACCESS-529 - fq param with spaces in call number browse returns HTTPClient::BadResponseError
https://culibrary.atlassian.net/browse/DACCESS-530 - Browse controller does not handle bad responses from Solr
https://culibrary.atlassian.net/browse/DACCESS-531 - Standardize Solr fetch code in browse controller

• Use rsolr instead of HTTPClient for connecting to solr from BrowseController (browse#index esp.) and for virtual call number browse on catalog record pages.
• Rescue RSolr::Error::Http using blacklight's default request error handling (#handle_request_error), which logs the error, redirects to browse#index, and displays a flash message.
• Dries up logic in browse#index to reuse solr browse logic across Author, Author-Title, Subject, Call-Number and virtual browse types.
• Remove library encoding in url in view so we're not double-encoding the param before sending to solr (rsolr already handles this)

If I had more time, I'd have written more tests to improve code coverage on this area of the code, but I was trying to hustle to include this in next week's sprint deploy. But I don't want to hold anything back, so if anything turns up in the PR review (or if it's too short notice to review this PR before deploy!), I can just sync with Jesi to see if this merits its own off-sprint deploy.