Add ability for throws annotation to accept variables

[lwasylow]

Would be good if the throws annotation allow to instead of hardocode number use a constant from other packages. Quite often the error numbers are defined in common package so that can be reused.
eg. - - %throws(schema.package.c_e_exception_no)

[jgebal]

There are in general 4 ways to pass an exception:

• By exception number

--%throws(-20000)
procedure test_that_raises_20000;

• by exception number variable

package my_exceptions is
  e_some_exception constant integer := -20000;
end;
/
--%throws(my_exceptions.e_some_exception_no)
procedure test_that_raises_20000;

• By exception variable

package my_exceptions is
  e_some_exception exception;
  pragma exception_init(e_some_exception, -20000);
end;
/
--%throws(my_exceptions.e_some_exception)
procedure test_that_raises_20000;

• by named exception

--%throws(NO_DATA_FOUND)
procedure test_that_raises_20000;

If we want to support variables, we should probably support both kinds (number/exception)
If we will go into effort of supporting exception type, we're actually already there to support named exceptions too.

Sample code:

create or replace package my_exceptions is
  e_some_exception exception;
  pragma exception_init(e_some_exception, -20000);
  e_other_exception constant integer := -20000;
end;
/

declare
    procedure check_var(a_var varchar2) is
      a varchar2(250);
      b varchar2(250);
      c varchar2(250);
      dblink varchar2(250);
      next_pos pls_integer;
    begin
      --check if it is a number first
      dbms_utility.name_tokenize(a_var, a, b, c, dblink, next_pos);
      --check if it is a predefined exception
      begin
        execute immediate 'begin null; exception when '||a_var||' then null; end;';
        dbms_output.put_line(a_var||' is a named exception');
      exception
        when others then
          if dbms_utility.format_error_stack() like '%PLS-00485%' then
            execute immediate 'declare x positiven := -('||a_var||'); begin null; end;';
            dbms_output.put_line(a_var||' is a negative number');
            --- then what?
          end if;
      end;
    end;
begin
  check_var('my_exceptions.e_some_exception');
  check_var('my_exceptions.e_other_exception');
  check_var('no_data_found');
--  check_var('-20000');
end;
/