add readobj decoding for FDO dlopen metadata

Note owner: FDO
Note type: 0x407c0c0a
Note data: JSON text

Example output -- llvm-readobj currently prints:
```
$ llvm-readelf -n FirstDriverStation
...
Displaying notes found in: .note.dlopen
Owner Data size Description
FDO 0x00000087 Unknown note type: (0x407c0c0a)
description data: 5b 7b 22 66 65 61 74 75 72 65 22 3a 22 68 69 64 61 62 69 2d 6c 69 62 75 73 62 22 2c 22 64 65 73 63 72 69 70 74 69 6f 6e 22 3a 22 53 75 70 70 6f 72 74 20 66 6f 72 20 6a 6f 79 73 74 69 63 6b 73 20 74 68 72 6f 75 67 68 20 6c 69 62 75 73 62 22 2c 22 70 72 69 6f 72 69 74 79 22 3a 22 73 75 67 67 65 73 74 65 64 22 2c 22 73 6f 6e 61 6d 65 22 3a 5b 22 6c 69 62 75 73 62 2d 31 2e 30 2e 73 6f 2e 30 22 5d 7d 5d 00
...
```

GNU readelf prints:
```
$ /usr/local/bin/readelf -n FirstDriverStation
...
Displaying notes found in: .note.dlopen
Owner Data size Description
FDO 0x00000087 FDO_DLOPEN_METADATA
Dlopen Metadata: [{"feature":"hidabi-libusb","description":"Support for joysticks through libusb","priority":"suggested","soname":["libusb-1.0.so.0"]}]
```

Start with llvm-readobj's note-display handling and compare the provided .note.dlopen output with GNU readelf. Trace how note owners and types are decoded, then add recognition for the FDO type 0x407c0c0a so the JSON payload is shown as Dlopen Metadata; done means the example no longer reports an unknown note type.

Written by the indexing model from the issue text.