[PAC][lld][AArch64][ELF] Support signed GOT with tiny code model (#113816)
Depends on #114525
Support `R_AARCH64_AUTH_GOT_ADR_PREL_LO21` and `R_AARCH64_AUTH_GOT_LD_PREL19`
GOT-generating relocations. A corresponding `RE_AARCH64_AUTH_GOT_PC` member
of `RelExpr` is added, which is an AUTH-specific variant of `R_GOT_PC`.