info: show Linux formulae details and analytics

- This makes use of the new /api/formula-linux and /api/analytics-linux
  endpoints in formulae.brew.sh to give Linux users up to date formula and
  analytics info for their installed core formulae.

Before, on Linux, the macOS stats for the `ack` formula:

```
$ brew info ack
[...]
==> Analytics
install: 12,422 (30 days), 32,742 (90 days), 97,788 (365 days)
install_on_request: 10,778 (30 days), 28,339 (90 days), 85,202 (365 days)
build_error: 0 (30 days)
```

Now, on Linux, the Linux stats for the `ack` formula:

```
$ brew info ack
[...]
==> Analytics
install: 95 (30 days), 242 (90 days), 737 (365 days)
install_on_request: 94 (30 days), 241 (90 days), 734 (365 days)
build_error: 0 (30 days)
```

Library/Homebrew/cmd/info.rb

@@ -368,7 +368,7 @@ module Homebrew
   end
 
   def output_formula_analytics(f)
-    json = formulae_api_json("formula/#{f}.json")
+    json = formulae_api_json("#{formula_path}/#{f}.json")
     return if json.blank? || json["analytics"].blank?
 
     full_analytics = args.analytics? || args.verbose?
@@ -431,4 +431,16 @@ module Homebrew
   def format_percent(percent)
     format("%<percent>.2f", percent: percent)
   end
+
+  def formula_path
+    "formula"
+  end
+  alias_method :generic_formula_path, :formula_path
+
+  def analytics_path
+    "analytics"
+  end
+  alias_method :generic_analytics_path, :analytics_path
+
+  require "extend/os/cmd/info"
 end

Library/Homebrew/extend/os/cmd/info.rb

@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require "extend/os/linux/info" if OS.linux?

Library/Homebrew/extend/os/linux/info.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module_function
+
+  def formula_path
+    return generic_formula_path if ENV["HOMEBREW_FORCE_HOMEBREW_ON_LINUX"]
+
+    "formula-linux"
+  end
+
+  def analytics_path
+    return generic_analytics_path if ENV["HOMEBREW_FORCE_HOMEBREW_ON_LINUX"]
+
+    "analytics-linux"
+  end
+end