[PAC][ELF] Support .note.gnu.property for marking schema

[kovdan01]

ARM-software/abi-aa#240 changes PAuthABIELF64 a bit. Main changes:

• GNU property becomes the main way of ELF marking, separate note section becomes an alternative;

• Compatibility info is restricted to <platform, version> tuple only (8+8=16 bytes) w/o extra info previously allowed.

Changes to be applied:

• Support related constants access-softek/llvm-project@c8d71df

• Frontend support access-softek/llvm-project@a0cc186

• Backend support access-softek/llvm-project@a3ddb4e

• LLD support access-softek/llvm-project@e4ff3bf

[kovdan01]

Tagging @asl

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

Author: Daniil Kovalev (kovdan01)

https://github.com/ARM-software/abi-aa/pull/240 changes PAuthABIELF64 a bit. Main changes:

• GNU property becomes the main way of ELF marking, separate note section becomes an alternative;

• Compatibility info is restricted to <platform, version> tuple only (8+8=16 bytes) w/o extra info previously allowed.

Changes to be applied:

• Support related constants access-softek/llvm-project@c8d71df

• Frontend support access-softek/llvm-project@a0cc186

• Backend support access-softek/llvm-project@a3ddb4e

• LLD support access-softek/llvm-project@e4ff3bf

[kovdan01]

Close as completed:

• Support related constants [PAC][llvm-readobj][AArch64][ELF] Support GNU_PROPERTY_AARCH64_FEATURE_PAUTH #85231
• Frontend support [AArch64][PAC][clang][ELF] Support PAuth ABI core info #85235
• Backend support [AArch64][PAC][MC][ELF] Support PAuth ABI compatibility tag #85236
• LLD support [lld][AArch64][ELF][PAC] Support AUTH relocations and AUTH ELF marking #72714