expose utils from extism, particularly logging

[nilslice]

very convenient to have a function like:

/// Logs format string to host, if log level is enabled.
pub fn log(level: comptime_int, comptime fmt: []const u8, args: anytype) !void {
    const msg = try std.fmt.allocPrint(_plugin.allocator, fmt, args);
    _plugin.log(@enumFromInt(level), msg);
}

Which is better if we have pub LogLevel in Extism zig-pdk, among other changes: extism/zig-pdk#37