[pauthabielf64] Define `NT_ARM_TYPE_PAUTH_ABI_TAG` constant

[kovdan01]

In section 14.1 of pauthabielf64 we have the following https://github.com/ARM-software/abi-aa/blob/main/pauthabielf64/pauthabielf64.rst#141default-marking-schema:

A new section named .note.AARCH64-PAUTH-ABI-tag of type SHT_NOTE is defined ... The type field shall be 1

In LLVM, we proposed a corresponding constant NT_ARM_TYPE_PAUTH_ABI_TAG equal to 1: see https://github.com/llvm/llvm-project/pull/74874. The pauthabielf64 should also contain the constant name to have things consistent. See discussion in https://github.com/llvm/llvm-project/pull/72713#discussion_r1423746772