server : escape the special tokens without std::regex (#30243)
The d1-omni and kev prompts escape "<|name|>" in the request text with
std::regex_replace. libstdc++ recurses for each char of the name, so a
state of "<|" and 30000 letters overflows the stack of the HTTP thread
and llama-server dies with SIGSEGV.
server_decision_escape_special_tokens() writes the same text with a loop.
test-server-component compares it with the regex on every string of up to
6 chars of "<|>a-".