Extend niceql to Arel

[NikolayRys]

In this PR I'm doing several things, and the primary one - I'm fixing the way how it is included in ActiveRecord. Currently, it has been missing Arel, which has to_sql methods too. Niceql would be a perfect addition there.

I have removed 2 and added 2 other classes to make the inclusion more comprehensive and consistent.

1. Removed ActiveRecord:Base - it doesn't have to_sql method

development(main)> User.niceql
NameError: undefined local variable or method `to_sql' for #<Class:0x00007f836610cea8>
Did you mean?  to_s
from /Users/nikolay/.rvm/gems/ruby-2.7.2/gems/activerecord-6.0.4.1/lib/active_record/dynamic_matchers.rb:22:in `method_missing'

2. Removed ActiveRecord::Associations::CollectionProxy because it uses the same implementation as Relation:

development(main)> Attendee.last.ad_clicks.method(:to_sql).source_location
=> ["/Users/nikolay/.rvm/gems/ruby-2.7.2/gems/activerecord-6.0.4.1/lib/active_record/relation.rb", 651]

3. Added Arel::TreeManager: https://github.com/rails/rails/blob/main/activerecord/lib/arel/tree_manager.rb#L49
4. Added Arel::Nodes::Node: https://github.com/rails/rails/blob/main/activerecord/lib/arel/nodes/node.rb#L39

Also, I think that extract_err_caret_line is meant to be a private method.

[NikolayRys]

you don't need to specify database here, otherwise, it creates a file and it's not in-memory anymore

[alekseyl]

yep, indeed.

[alekseyl]

looks neat!