Minimize imports in an effort to lower simulation setup time

These changes represent a 21% reduction of execution time for the 460 test cases in hdl-modules repo: https://github.com/hdl-modules/hdl-modules
For some small testbenches, the reduction is as much as 42%.
Note that this repo contains only small to medium sized testbenches (1-10 seconds, with most around 1-4 seconds).

This is all using the GHDL simulator with GCC backend on Linux. With ModelSim Intel FPGA starter edition 2020.1, the reductions is negligible (1-2%).

This change:

1. Stop using "context" in all VUnit packages.
   In most packages, importing with context includes a lot more than what is actually used.

2. Stop using "use work.x_pkg.all" in cases where only 1-3 things are used from the package.
   Instead, one explicit "use" clause for the things that are actually used.

   * Not done for the most common packages (run_pkg, check_pkg, logger_pkg).

   * Not done for includes from very small packages.

3. For packages that have head and body in different files, move all imports to the head file.
   As they were, split between the files, there was a lot of overlap of imports, and it what hard to get an overview of what is actually imported and what is actually used.

The first point represents roughly 80% of the performance gain.

Note that in order to reach the performance gains listed above, the corresponding changes have to be made to all testbenches and simulation code in the user repo also.
If the testbench includes "vunit_context", "com_context" etc, the performance gains will not be realized since everything will be imported anyway.

Author: LukasVik

vunit/vhdl/check/src/check.vhd

@@ -6,15 +6,6 @@
 --
 -- Copyright (c) 2014-2024, Lars Asplund lars.anders.asplund@gmail.com
 
-library ieee;
-use ieee.std_logic_1164.all;
-use ieee.numeric_std.all;
-use std.textio.all;
-use work.checker_pkg.all;
-use work.string_ops.all;
-use work.location_pkg.all;
-use work.integer_vector_ptr_pkg.all;
-
 package body check_pkg is
   type boolean_vector is array (natural range <>) of boolean;
 

vunit/vhdl/check/src/check_api.vhd

@@ -10,12 +10,16 @@
 library ieee;
 use ieee.std_logic_1164.all;
 use ieee.numeric_std.all;
+
 use std.textio.all;
+
 use work.checker_pkg.all;
-use work.logger_pkg.all;
+use work.event_common_pkg.any_event_t;
+use work.event_common_pkg.notify;
+use work.integer_vector_ptr_pkg.all;
 use work.log_levels_pkg.all;
+use work.logger_pkg.logger_t;
 use work.string_ops.all;
-use work.event_common_pkg.all;
 use work.string_ptr_pkg.all;
 
 package check_pkg is

vunit/vhdl/com/src/com.vhd

@@ -9,18 +9,12 @@
 library ieee;
 use ieee.std_logic_1164.all;
 
-context work.vunit_context;
-
-use work.queue_pkg.all;
-use work.queue_2008p_pkg.all;
-use work.queue_pool_pkg.all;
-use work.integer_vector_ptr_pkg.all;
-use work.string_ptr_pkg.all;
-use work.codec_pkg.all;
-use work.com_support_pkg.all;
-use work.com_messenger_pkg.all;
 use work.com_common_pkg.all;
+use work.com_messenger_pkg.all;
+use work.com_support_pkg.all;
 use work.logger_pkg.all;
+use work.queue_pkg.all;
+use work.queue_pool_pkg.all;
 
 use std.textio.all;
 

vunit/vhdl/com/src/com_api.vhd

@@ -11,11 +11,9 @@ library ieee;
 use ieee.std_logic_1164.all;
 
 use work.com_types_pkg.all;
-use work.queue_pkg.all;
-use work.integer_vector_ptr_pkg.all;
-use work.string_ptr_pkg.all;
-use work.id_pkg.all;
-use work.event_private_pkg.all;
+use work.id_pkg.id_t;
+use work.event_private_pkg.new_basic_event;
+use work.event_private_pkg.com_net_event;
 
 package com_pkg is
   -- Global predefined network. See network_t description in com_types.vhd for

vunit/vhdl/com/src/com_common.vhd

@@ -9,10 +9,11 @@
 library ieee;
 use ieee.std_logic_1164.all;
 
-use work.com_messenger_pkg.all;
-use work.com_types_pkg.all;
-use work.event_common_pkg.all;
-use work.event_private_pkg.all;
+use work.com_messenger_pkg.messenger_t;
+use work.com_types_pkg.com_status_t;
+use work.event_common_pkg.notify;
+use work.event_common_pkg.is_active;
+use work.event_private_pkg.basic_event_t;
 
 package com_common_pkg is
   shared variable messenger :       messenger_t;

vunit/vhdl/com/src/com_debug_codec_builder.vhd

@@ -6,11 +6,10 @@
 --
 -- Copyright (c) 2014-2024, Lars Asplund lars.anders.asplund@gmail.com
 
-library vunit_lib;
-context vunit_lib.vunit_context;
-
 use std.textio.all;
 
+use work.string_ops.all;
+
 package com_debug_codec_builder_pkg is
   -----------------------------------------------------------------------------
   -- Encoding support

vunit/vhdl/com/src/com_messenger.vhd

@@ -12,7 +12,6 @@ use work.com_support_pkg.all;
 use work.queue_pkg.all;
 use work.queue_pool_pkg.all;
 use work.string_ptr_pkg.all;
-use work.codec_pkg.all;
 use work.logger_pkg.all;
 use work.log_levels_pkg.all;
 use work.id_pkg.all;

vunit/vhdl/com/src/com_support.vhd

@@ -4,8 +4,9 @@
 --
 -- Copyright (c) 2014-2024, Lars Asplund lars.anders.asplund@gmail.com
 
-context work.vunit_context;
 use work.com_types_pkg.all;
+use work.logger_pkg.all;
+use work.string_ops.all;
 
 package com_support_pkg is
 

vunit/vhdl/com/src/com_types.vhd

@@ -24,7 +24,7 @@ use work.queue_pkg.all;
 use work.queue_2008p_pkg.all;
 use work.queue_pool_pkg.all;
 use work.dict_pkg.all;
-use work.event_private_pkg.all;
+use work.event_private_pkg.basic_event_t;
 
 package com_types_pkg is
 

vunit/vhdl/core/src/core_pkg.vhd

@@ -5,6 +5,7 @@
 -- Copyright (c) 2014-2024, Lars Asplund lars.anders.asplund@gmail.com
 
 use std.textio.all;
+
 use work.stop_pkg;
 use work.integer_vector_ptr_pkg.all;
 use work.string_ptr_pkg.all;