docs: Migrating Scoped Dir Access preview docs into DAC

  to: /training/tv/tif/content-recording.html

- from: /preview/features/direct-boot.html

  to: /training/articles/direct-boot.html

- from: /preview/features/scoped-folder-access.html

  to: /training/articles/scoped-directory-access.html

save to the external storage. All applications can read and write files placed on the external

storage and the user can remove them.</p>

<h3 id="ScopedDirAccess">Using Scoped Directory Access</h3>

On Android 7.0 or later, if you need access to a specific directory on

external storage, use scoped directory access. Scoped directory access

simplifies how your application accesses standard external storage directories,

such as the <code>Pictures</code> directory, and provides a simple

permissions UI that clearly details what directory the application is

requesting access to. For more details on scoped directory access, see

<a href="{@docRoot}training/articles/scoped-directory-access.html">Using

Scoped Directory Access</a>.

<h3 id="ExternalPermissions">Getting access to external storage</h3>

<p>In order to read or write files on the external storage, your app must acquire the