perf session: Add host_env argument to perf_session__new

perf session: Add host_env argument to perf_session__new

When creating a perf_session the host perf_env may or may not want to
be used. For example, `perf top` uses a host perf_env while `perf
inject` does not. Add a host_env argument to perf_session__new so that
sessions requiring a host perf_env can pass it in. Currently if none
is specified the global perf_env variable is used, but this will
change in later patches.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250724163302.596743-14-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>