fuzzgen: Always generate reachable blocks (#5034)

* fuzzgen: Always reachable blocks

* fuzzgen: Rename BlockTerminator

* fuzzgen: Rename `finalize_block`

* fuzzgen: Use `cloned` instead of map clone

Thanks @jameysharp!

Co-authored-by: Jamey Sharp <jamey@minilop.net>

* fuzzgen: `rustfmt`

* fuzzgen: Document paramless targets

* fuzzgen:  Add `BlockTerminatorKind`

* fuzzen: Update BrTable/Switch comment

* fuzzgen: Minor cleanup

Co-authored-by: Jamey Sharp <jamey@minilop.net>

cranelift/codegen/src/ir/jumptable.rs

@@ -33,6 +33,10 @@ impl JumpTableData {
             table: Vec::with_capacity(capacity),
         }
     }
+    /// Create a new jump table with the provided blocks
+    pub fn with_blocks(table: Vec<Block>) -> Self {
+        Self { table }
+    }
 
     /// Get the number of table entries.
     pub fn len(&self) -> usize {