feat: Improve Report API performance

[pranavrajs]

• Re-write the methods for clarity
• Remove the dependency on the ReportHelper class.
• Remove n+1 queries in the average metric time series data.

[pranavrajs]

Code Climate issue can be ignored as we will remove the reports_helper in the subsequent PRs.

[sentry-io[bot]]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ ActiveRecord::QueryCanceled: PG::QueryCanceled: ERROR: canceling statement due to statement timeout (ActiveRecord::QueryCance... Api::V2::Accounts::ReportsController#index View Issue
• ‼️ NoMethodError: undefined method `to_sym' for nil:NilClass (NoMethodError) Api::V2::Accounts::ReportsController#summary View Issue
• ‼️ NoMethodError: undefined method `to_sym' for nil:NilClass (NoMethodError) Api::V2::Accounts::ReportsController#index View Issue
• ‼️ Date::Error: invalid date (Date::Error) Api::V2::Accounts::ReportsController#index View Issue
• ‼️ Date::Error: invalid date (Date::Error) Api::V2::Accounts::ReportsController#index View Issue

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