Change proposal to use annotation instead of special syntax

This shows that we don't really need any new syntax for handling the choice of solver method, at the cost of having this important information hidden away in an annotation.

RationaleMCP/0031/annotations.md

@@ -38,6 +38,7 @@ These are all the non-vendor specific annotations inherited from full Modelica t
 
 These are the new annotations introduced in Flat Modelica, each explained in more detail below:
 - [`Protected`](#protected) — Indicate whether component declaration comes from protected section in original full Modelica model
+- [`solverMethod`](#solvermethod) — Discretization method for a clocked sub-partition
 
 
 ### `Protected`
@@ -103,6 +104,17 @@ package 'M'
 end 'M';
 ```
 
+### `solverMethod`
+
+Form:
+```
+String solverMethod = "ImplicitEuler";
+```
+
+The `solverMethod` annotation is only allowed on a `subpartition`.
+The recognized method names are the same as for the `solverMethod` named argument of the `Clock` constructor in full Modelica.
+
+
 
 ## Vendor annotations
 

RationaleMCP/0031/differences.md

@@ -1272,7 +1272,7 @@ partition /* Beginning of base-partition */
     'baseVar' = sample('x');
 
   subpartition
-    discretization "ImplicitEuler";
+    annotation(solverMethod = "ImplicitEuler");
     Clock _subClock0 = subSample('baseClock', 2); /* Automatically generated clock name. */
   equation
     der('cVar1') = noClock('baseVar');

RationaleMCP/0031/grammar.md

@@ -185,7 +185,6 @@ end _F;
 > _sub-partition_ →\
 >   **subpartition** _string-comment_\
 >   ( _annotation-comment_ **;** )?
->   ( **discretization** _STRING_ **;** )?\
 >   _clock-clause_ **;**\
 >   ( **equation** ( _equation_ **;** )* \
 >   | **algorithm** ( _statement_ **;** )* \