Delegate application record generator description to orm hooked generator.

[gmcgibbon]

Motivation / Background

Delegates usage docs for bin/rails g application_record to the ORM-hooked generator (by default Active Record).

Detail

This allows ORM-hooked app record generators to specify their own usage descriptions.

Before:

% bin/rails g application_record -h
Running via Spring preloader in process 36026
Usage:
  rails generate application_record [options]

Options:
      [--skip-namespace], [--no-skip-namespace]              # Skip namespace (affects only isolated engines)
      [--skip-collision-check], [--no-skip-collision-check]  # Skip collision check
  -o, --orm=NAME                                             # ORM to be invoked
                                                             # Default: active_record

Runtime options:
  -f, [--force]                    # Overwrite files that already exist
  -p, [--pretend], [--no-pretend]  # Run but do not make any changes
  -q, [--quiet], [--no-quiet]      # Suppress status output
  -s, [--skip], [--no-skip]        # Skip files that already exist

Description:
    Create rails files for application_record generator.

After:

% bin/rails g application_record -h
Running via Spring preloader in process 36172
Usage:
  rails generate application_record [options]

Options:
      [--skip-namespace], [--no-skip-namespace]              # Skip namespace (affects only isolated engines)
      [--skip-collision-check], [--no-skip-collision-check]  # Skip collision check
  -o, --orm=NAME                                             # ORM to be invoked
                                                             # Default: active_record

Runtime options:
  -f, [--force]                    # Overwrite files that already exist
  -p, [--pretend], [--no-pretend]  # Run but do not make any changes
  -q, [--quiet], [--no-quiet]      # Suppress status output
  -s, [--skip], [--no-skip]        # Skip files that already exist

Description:
    Generates an `ApplicationRecord` base class for other models to inherit from.

Example:
    `bin/rails generate application_record`

    This generates the base class. A test is not generated because no
    behaviour is included in `ApplicationRecord` by default.

Additional information

Similar to the work done to delegate generator descriptions to the ORM-hooked model generator in #45315

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• There are no typos in commit messages and comments.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Feature branch is up-to-date with main (if not - rebase it).
• Pull request only contains one commit for bug fixes and small features. If it's a larger feature, multiple commits are permitted but must be descriptive.
• Tests are added if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.
• PR is not in a draft state.
• CI is passing.