Refactor of usage dashboard (moved logic from JS to Ruby)

[briri]

Fixes #2083, #2116, #2119

Decided to refactor the usage dashboard code while in fixing these tickets. The discrepancies we were seeing with the numbers were due to the fact that some of the code was calling the API and the others were pulling data from the stat table (which they should all be doing).

• Broke the large index.html.erb file into smaller partials
• Moved as much logic from the JS to the usage_controller.rb
• Added a policy file for the controller
• Moved the generic chart rendering JS into a utils/charts.js file
• Removed ajax calls from JS and replaced with Rails pattern to render a js.erb instead.
• Changed buttons to links with the new 'opens in a new window' accessibility feature
• Removed references to and need for API token in the usage dashboard
• Added tests for all new code

[github-actions]

Remaining comments which cannot be posted as a review comment to avoid GitHub Rate Limit

rubocop

app/helpers/usage_helper.rb|50 col 33| Lint/UnusedBlockArgument: Unused block argument - k. If it's necessary, use _ or _k as an argument name to indicate that it won't be used. (https://rubystyle.guide#underscore-unused-vars)
app/helpers/usage_helper.rb|55 col 3| Metrics/AbcSize: Assignment Branch Condition size for plans_per_template_ranges is too high. [<0, 20, 0> 20/15] (http://c2.com/cgi/wiki?AbcMetric, https://en.wikipedia.org/wiki/ABC_Software_Metric)
app/helpers/usage_helper.rb|57 col 10| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|58 col 10| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|59 col 10| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|60 col 10| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|61 col 10| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|70 col 45| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|71 col 46| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/helpers/usage_helper.rb|77 col 31| Style/StringLiterals: Prefer double-quoted strings unless you need single quotes to avoid extra backslashes for escaping. (https://rubystyle.guide#consistent-string-literals)
app/models/stat.rb|37 col 17| Style/SymbolArray: Use %i or %I for an array of symbols. (https://rubystyle.guide#percent-i)
app/models/stat_created_plan.rb|24 col 8| Style/RedundantSelf: Redundant self detected. (https://rubystyle.guide#no-self-unless-required)
app/models/stat_created_plan.rb|24 col 33| Style/RedundantSelf: Redundant self detected. (https://rubystyle.guide#no-self-unless-required)
app/models/stat_created_plan.rb|31 col 3| Lint/ToJSON: #to_json requires an optional argument to be parsable via JSON.generate(obj).
app/policies/usage_policy.rb|3 col 21| Style/StructInheritance: Don't extend an instance initialized by Struct.new. Use a block to customize the struct. (https://rubystyle.guide#no-extend-struct-new)
app/policies/usage_policy.rb|4 col 1| Layout/EmptyLinesAroundClassBody: Empty line missing at class body beginning. (https://rubystyle.guide#empty-lines-around-bodies)
app/policies/usage_policy.rb|6 col 24| Lint/UnusedMethodArgument: Unused method argument - usage. If it's necessary, use _ or _usage as an argument name to indicate that it won't be used. (https://rubystyle.guide#underscore-unused-vars)
app/policies/usage_policy.rb|7 col 5| Layout/EmptyLineAfterGuardClause: Add empty line after guard clause.

[xsrust]

Thanks for the cleanup here @briri

I think moving the logic over to ruby will make this a lot more maintainable for our current team.

[briri]

made some changes based on @raycarrick-ed feedback in #2083.

• Removed the class that was making the 'opens in a new window' message appear with the download buttons
• Moved the Org selection box of the filter down to its own row