Update Rails, Ruby, and add ruby debug gem

[ahangarha]

In this PR:

• Updated Rails to version 7+
• Fixed builder missing template error
• Added debug gem

Possible todos:

• Update node version to 18.13.0 (LTS)
• Update Ruby version to the latest: 3.2
  Our CI still doesn't support Ruby 3.2.0
• Update docker files
• Update README
• Update docs (jbuilder)
• Update changelog?
  Closes Update Rails 7, Ruby 3.1, and add ruby-debug gem #515

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This change is 

[justin808]

Did you follow the steps at https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-6-1-to-rails-7-0?

[ahangarha]

@justin808
I followed the mentioned upgrade guideline. Just there are two concerns:

• Updating cache serialization format doesn't work. I couldn't make the test pass for this change so I omitted this change.
• There is a new change in test environment config file related to eager loading. Since I was not sure about the right value, I kept the old value to work and added the new code as a comment.
• I noticed an inconsistency in our CI tests. The same changes could sometimes pass and sometimes fail. Namely, the commit d825126 here (which passes the CI) failed twice at first. I removed the commit and made it again and it failed. I reran the CI and it passed. I am not sure what causes this issue but as per the log, it could be related to rspec-rails version.

Let me know if I should update changelog. As I see, it is not updated for a very long time.

[ahangarha]

Few more concerns:

• Our Jbuilder doc file needs to be updated. I edited the to be the same way used in pages_controller. I added a new react component in erb one of our views but it didn't work. (though I generated the correct data but the component failed in getting rendered on the page. This needs further investigation.
• What to do with Travis config? It is very outdated and I think we can remove it.
• It seems we don't use Codeship anymore. If so, let's remove the badge on README file and also its outdated documentation.
• It seems our Gemnasium badge is broken.