[yaml2obj][elf2yaml] - Add a support for the `EntSize` field for `SHT_HASH` sections.

Specification  for SHT_HASH table says (https://refspecs.linuxbase.org/elf/gabi4+/ch5.dynamic.html#hash)
that it contains Elf32_Word entries for both 32/64 bit objects.

Currently both GNU linkers and LLD sets the `sh_entsize` field to `4`.

At the same time, `yaml2obj` ignores the `EntSize` field for SHT_HASH sections.
This patch fixes this and also adds a support for obj2yaml: it will not
dump this field when the `sh_entsize` contains the default value (`4`).

Differential revision: https://reviews.llvm.org/D88652