USDT: normalize names for STATE_ENTER

[moonchen]

STATE_ENTER passed &HttpSM::<state> straight through as the USDT probe
name, so the probes were emitted with names like:

&HttpSM::state_read_client_request_header
&HttpSM::tunnel_handler_post

The & and :: characters are illegal in USDT probe names — bpftrace
and perf treat : as the provider/name field separator and reject &
— so these ~41 probes could not be attached by name at all.

This passes the bare handler name from each call site and prepends the
prefix inside the macro, producing valid names that share a common
wildcard:

state_enter_state_read_client_request_header
state_enter_tunnel_handler_post

bpftrace -e 'usdt:.../traffic_server:trafficserver:state_enter_* {
    printf("sm=%d %s\n", arg0, probe); }'

It also fixes a &HttpSM : typo (STATE_ENTER for state_cache_open_write)
that had collapsed one probe to a bare &HttpSM. The debug log is
unchanged in meaning ([state_read_client_request_header, EVENT]).

The broken names were introduced by #11769; this is independent of the
in-flight USDT work in #13344.

[Copilot]

Pull request overview

This PR fixes ATS USDT probe naming for STATE_ENTER in HttpSM so probe names no longer contain illegal characters (&, ::) and can be attached by tools like bpftrace/perf.

Changes:

• Update the STATE_ENTER macro to emit probes with a state_enter_ prefix and a normalized handler/state token.
• Update all STATE_ENTER call sites in HttpSM.cc to pass the bare handler/state name (and fix the &HttpSM : typo at state_cache_open_write).