[yaml2obj] - Support reading a content as an array of bytes using the new 'ContentArray' key.

It implements the way to describe a section content using a multi line description. E.g:

```
- Name:         .foo
  Type:         SHT_PROGBITS
  ContentArray: [ 0x11, 0x22, 0x33, 0x44,                                ## .long 11223344
                  0x55, 0x66,                                            ## .short 5566.
                  0x77,                                                  ## .byte 0x77
                  0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF, 0x00 ] ## .quad 0x8899aabbccddeeff
```

It was briefly discussed in D75123 thread previously.

Differential revision: https://reviews.llvm.org/D82366