Add error/warning suppression with suppress_msg and unsuppress_msg commands (#157)

* Add error/warning suppression with `suppress_msg` and `unsuppress_msg` commands

* Fixes

* Merge docs

* Fixes

* Remove optional arg from class

* Add where to find message codes

* Update docs

* Requested fixes

* Deal with errors on the TCL side instead of C++ side

* Update ok file

* Add back in C++ side error suppression and have tests for both C++/TCL side suppression

* Requested fixes to ChangeLog and unifying suppression in C++/TCL

* Requested fixes

* Requested test adjustments

* Smallfixes

* Smallfixes

* Another smallfix

test/regression_vars.tcl

@@ -135,6 +135,7 @@ record_sta_tests {
   report_checks_src_attr
   report_json1
   report_json2
+  suppress_msg
   verilog_attribute
 }
 

test/suppress_msg.ok

@@ -0,0 +1,12 @@
+Warning: suppress_msg.tcl line 18, cmd warn 1
+caught Error: suppress_msg.tcl line 18, cmd error 1
+Warning: cmd warn 2
+caught Error: cmd error 2
+after error
+caught 
+caught 
+after error
+Warning: suppress_msg.tcl line 51, cmd warn 7
+caught Error: suppress_msg.tcl line 51, cmd error 7
+Warning: cmd warn 8
+caught Error: cmd error 8

test/suppress_msg.tcl

@@ -0,0 +1,56 @@
+# suppress and unsuppress message ids
+
+# Run sta_warn/sta_error to test TCL side suppression
+proc sta_cmd { msg } {
+  sta::sta_warn 1 "cmd warn $msg"
+  sta::sta_error 2 "cmd error $msg"
+  puts "after error"
+}
+
+# Run report_warn/report_error to test C++ side suppression
+proc report_cmd { msg } {
+  sta::report_warn 1 "cmd warn $msg"
+  sta::report_error 2 "cmd error $msg"
+  puts "after error"
+}
+
+# Ensure that TCL side messages are displayed as usual
+catch { sta_cmd 1 } error
+puts "caught $error"
+
+# Ensure that C++ side messages are displayed as usual
+catch { report_cmd 2 } error
+puts "caught $error"
+
+# Suppress messages
+suppress_msg 1 2
+
+# Ensure that TCL side messages are suppressed
+catch { sta_cmd 3 } error
+puts "caught $error"
+
+# Ensure that C++ side messages are suppressed
+catch { report_cmd 4 } error
+puts "caught $error"
+
+# Continue on error to avoid having to catch
+set sta_continue_on_error 1
+
+# Ensure that TCL side messages are suppressed
+# TCL side will make it to "after error"
+sta_cmd 5
+
+# Ensure that C++ side messages are suppressed
+# C++ will not make it to "after error" as the whole cmd is cancelled
+report_cmd 6
+
+# Unsuppress messages
+unsuppress_msg 1 2
+
+# Ensure that TCL side messages are displayed as usual
+catch { sta_cmd 7 } error
+puts "caught $error"
+
+# Ensure that C++ side messages are displayed as usual
+catch { report_cmd 8 } error
+puts "caught $error"