[DocsUI Peek] Metadata contents

Add basic metadata section:
- Size
- MIME Type
- Date modified

Applies to all file items, including folders:
- Size: 1 block (4096 bytes)
- Type: Folder
- Date modified: as expected
Folder metadata will be updated in a later change.

Bug: 382163595
Flag: com.android.documentsui.flags.use_material3
Flag: com.android.documentsui.flags.use_peek_preview_ro
Test: com.android.documentsui.peek.MetadataViewTest

Change-Id: Ic9778ae849cff6f2bf1b4f391f3ff8f50d5489c3