Merge pull request #608 from billsacks/dbug_flag

Add dbug_flag namelist option and remove unused info_dbug

### Description of changes

(1) Add dbug_flag namelist option to control this flag in the code, rather than requiring source code changes to change this value

(2) Remove unused info_dbug flag

### Specific notes

Contributors other than yourself, if any:

CMEPS Issues Fixed (include github issue #):
- Resolves #607

Are changes expected to change answers? (specify if bfb, different at roundoff, more substantial) - No

Any User Interface Changes (namelist or namelist defaults changes)?
- Adds dbug_flag namelist variable
- Removes unused INFO_DBUG xml variable and info_dbug namelist variable

### Testing performed
Please describe the tests along with the target model and machine(s) 
If possible, please also added hashes that were used in the testing

Ran `SMS_Ld3_D_P8x1.f10_f10_mg37.X.green_gnu` with dbug_flag set at 0 (default) and 11.

Author: billsacks

cime_config/config_component.xml

@@ -2310,15 +2310,6 @@
     <desc>determine if per ice thickness category fields are passed from ice to ocean - DO NOT EDIT (set by MOM6)</desc>
   </entry>
 
-  <entry id="INFO_DBUG">
-    <type>integer</type>
-    <valid_values>0,1,2,3,4,5,6,7,8,9</valid_values>
-    <default_value>1</default_value>
-    <group>run_flags</group>
-    <file>env_run.xml</file>
-    <desc>level of debug output, 0=minimum, 1=normal, 2=more, 3=too much</desc>
-  </entry>
-
   <!-- Prerun/postrun custom script options -->
 
   <entry id="PRERUN_SCRIPT">

cime_config/namelist_definition_drv.xml

@@ -879,15 +879,27 @@
     </values>
   </entry>
 
-  <entry id="info_debug" modify_via_xml="INFO_DBUG">
+  <entry id="dbug_flag">
     <type>integer</type>
     <category>expdef</category>
     <group>MED_attributes</group>
     <desc>
-      Level of debug output, 0=minimum, 1=normal, 2=more, 3=too much (default: 1)
+      Level of debug output; higher values give progressively more output
+
+      Some example values (other values are also accepted)
+      - 0: no extra debug output
+      - 1: a bit of debug output
+      - 2: a bit more debug output
+      - 6: a moderate amount of debug output
+      - 11: a lot of debug output
+      - 21: a huge amount of debug output
+
+      Note that setting this to moderate - high values can lead to overwhelming amounts of output.
+
+      (Default: 0)
     </desc>
     <values>
-      <value>$INFO_DBUG</value>
+      <value>0</value>
     </values>
   </entry>