Add decoding of HID report descriptors

[martinling]

Adds decoding of HID report descriptors using the hidreport parser.

I've spent some time coming up with a human-readable summary format, which makes it clear which data can be found in which bits of each report, whilst omitting extraneous detail.

These summaries are shown in the detail pane when a HID report descriptor request is selected.

Since the test suite does not generate and check detailed summaries, a separate test is added, with a selection of test cases taken from various devices I've captured.

Keyboard example:

○ Input report (8 bytes):
├── Keyboard LeftControl: byte 0 bit 0
├── Keyboard LeftShift: byte 0 bit 1
├── Keyboard LeftAlt: byte 0 bit 2
├── Keyboard Left GUI: byte 0 bit 3 
├── Keyboard RightControl: byte 0 bit 4
├── Keyboard RightShift: byte 0 bit 5
├── Keyboard RightAlt: byte 0 bit 6
├── Keyboard Right GUI: byte 0 bit 7
├── Padding: byte 1
└── Array of 6 buttons: bytes 2-7 [Keyboard/Keypad usage 0x00 — Keyboard/Keypad usage 0xFF]

○ Output report (1 byte):
├── Num Lock: byte 0 bit 0
├── Caps Lock: byte 0 bit 1
├── Scroll Lock: byte 0 bit 2
├── Compose: byte 0 bit 3
├── Kana: byte 0 bit 4
└── Padding: byte 0 bits 5-7

Mouse example:

○ Input report #1 (7 bytes):
├── Button 1: byte 1 bit 0
├── Button 2: byte 1 bit 1
├── Button 3: byte 1 bit 2
├── Button 4: byte 1 bit 3
├── Button 5: byte 1 bit 4
├── Padding: byte 1 bits 5-7
├── X: byte 2 bit 0 — byte 3 bit 3 (values -2047 to 2047)
├── Y: byte 3 bit 4 — byte 4 bit 7 (values -2047 to 2047)
├── Wheel: byte 5 (values -127 to 127)
└── AC Pan: byte 6 (values -127 to 127)