Auto-sync with upstream branch release/2.36/master
    
    Upstream commit: 33f1b4c1452b33991e670f636ebe98b90a405e10
    
    - wcsmbs: Add missing test-c8rtomb/test-mbrtoc8 dependency
    - stdlib: Suppress gcc diagnostic that char8_t is a keyword in C++20 in uchar.h.
    - Create ChangeLog.old/ChangeLog.25. (tag: glibc-2.36)
    - Prepare for glibc 2.36 release.
    - Update install.texi, and regenerate INSTALL.
    - Update NEWS bug list.
    - Update libc.pot for 2.36 release.
    - tst-pidfd.c: UNSUPPORTED if we get EPERM on valid pidfd_getfd call
    - stdlib: Tuned down tst-arc4random-thread internal parameters
    - LoongArch: Add greg_t and gregset_t.
    - LoongArch: Fix VDSO_HASH and VDSO_NAME.
    - riscv: Update rv64 libm test ulps
    - riscv: Update nofpu libm test ulps
    
    No regressions seen in mass-prebuild of critical-path-base packages.