All changes:
- Include file.pack_libraries and file.unpack_libraries to the menu [1].
- Rename "Pack Blender Libraries" → "Pack Linked Libraries" [2].
- Rename "Unpack Blender Libraries" → "Unpack Linked Libraries" [2].
- Rename "Pack All Into .blend" → "Pack Resources" [3]
- Rename "Unpack All Into Files" → "Unpack Resources" [3]
- Rename "☑ Automatically Pack Into .blend" → "☑ Automatically Pack Resources" [3]
- Rename "Make All Paths Relative" → "Make Paths Relative" [4]
- Rename "Make All Paths Absolute" → "Make Paths Absolute" [4]
- Add separators accordingly
[1] - This was never exposed since its original commit rB16411da41e40. Now that operator not listed in menus don't
show up in the search, this became even more hidden.
[2] - The original name (Pack Blender Library) was not clear enough. Pose Libraries and Asset Libraries are also technically Blender libraries.
[3] - The term All was misleading since it didn't include the Linked Libraries.
[4] - No need to use "All". It is not used in the Report/Find Missing Files either.
This commit put this in the File > External Data menu.

