Rollup merge of #125754 - Zalathar:conditions-num, r=lqd

coverage: Rename MC/DC `conditions_num` to `num_conditions`

Updated version of #124571, without the other changes that were split out into #125108 and #125700.

This value represents a quantity of conditions, not an ID, so the new spelling is more appropriate.

Some of the code touched by this PR could perhaps use some other changes, but I would prefer to keep this PR as a simple renaming and avoid scope creep.

`@rustbot` label +A-code-coverage

compiler/rustc_middle/src/mir/coverage.rs

@@ -329,14 +329,14 @@ pub struct MCDCBranchSpan {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct DecisionInfo {
     pub bitmap_idx: u32,
-    pub conditions_num: u16,
+    pub num_conditions: u16,
 }
 
 #[derive(Clone, Debug)]
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct MCDCDecisionSpan {
     pub span: Span,
-    pub conditions_num: usize,
+    pub num_conditions: usize,
     pub end_markers: Vec<BlockMarkerId>,
     pub decision_depth: u16,
 }

compiler/rustc_middle/src/mir/pretty.rs

@@ -512,12 +512,12 @@ fn write_coverage_branch_info(
         )?;
     }
 
-    for coverage::MCDCDecisionSpan { span, conditions_num, end_markers, decision_depth } in
+    for coverage::MCDCDecisionSpan { span, num_conditions, end_markers, decision_depth } in
         mcdc_decision_spans
     {
         writeln!(
             w,
-            "{INDENT}coverage mcdc decision {{ conditions_num: {conditions_num:?}, end: {end_markers:?}, depth: {decision_depth:?} }} => {span:?}"
+            "{INDENT}coverage mcdc decision {{ num_conditions: {num_conditions:?}, end: {end_markers:?}, depth: {decision_depth:?} }} => {span:?}"
         )?;
     }