[php-src] PR #23227: perf: move EG() and CG() in ZTS builds into __thread storage

Pull Request: https://github.com/php/php-src/pull/23227 Author: henderkes replay of #22231 Moves EG and CG into __thread storage after all. We first moved them into constant offsets (#22287) from *_tsrm_ls_cache, but I couldn't find a way to stop gcc or clang from reloading _tsrm_ls_cache base pointer between function calls, leading to an extra pointer load once per function. This eliminates the pointer load, making the access sequence to EG/CG just a single mov (x64) / mrs + add + ldr (aarch64) under local-exec. initial-exec likewise loses the pointer load so 3 -> 2 instructions (x64). cc @arnaud-lb What I'm adding here to counter the global-dynamic fallback slowdown is the option to explicitly opt-in to initial-exec, under the knowledge that host programs loading it will need to increase the static tls surplus. This is not an issue for package providers. PS: Actually figured out that the explicit model choice doesn't happen for musl, not sure about IE (static tls surplus on musl?), but LE should work just fine. That's for another PR though.