Mass rename Ebb and relatives to Block (#1365)

* Manually rename BasicBlock to BlockPredecessor

BasicBlock is a pair of (Ebb, Inst) that is used to represent the
basic block subcomponent of an Ebb that is a predecessor to an Ebb.

Eventually we will be able to remove this struct, but for now it
makes sense to give it a non-conflicting name so that we can start
to transition Ebb to represent a basic block.

I have not updated any comments that refer to BasicBlock, as
eventually we will remove BlockPredecessor and replace with Block,
which is a basic block, so the comments will become correct.

* Manually rename SSABuilder block types to avoid conflict

SSABuilder has its own Block and BlockData types. These along with
associated identifier will cause conflicts in a later commit, so
they are renamed to be more verbose here.

* Automatically rename 'Ebb' to 'Block' in *.rs

* Automatically rename 'EBB' to 'block' in *.rs

* Automatically rename 'ebb' to 'block' in *.rs

* Automatically rename 'extended basic block' to 'basic block' in *.rs

* Automatically rename 'an basic block' to 'a basic block' in *.rs

* Manually update comment for `Block`

`Block`'s wikipedia article required an update.

* Automatically rename 'an `Block`' to 'a `Block`' in *.rs

* Automatically rename 'extended_basic_block' to 'basic_block' in *.rs

* Automatically rename 'ebb' to 'block' in *.clif

* Manually rename clif constant that contains 'ebb' as substring to avoid conflict

* Automatically rename filecheck uses of 'EBB' to 'BB'

'regex: EBB' -> 'regex: BB'
'$EBB' -> '$BB'

* Automatically rename 'EBB' 'Ebb' to 'block' in *.clif

* Automatically rename 'an block' to 'a block' in *.clif

* Fix broken testcase when function name length increases

Test function names are limited to 16 characters. This causes
the new longer name to be truncated and fail a filecheck test. An
outdated comment was also fixed.

cranelift/bforest/src/lib.rs

@@ -148,22 +148,22 @@ mod tests {
     use super::*;
     use crate::entity::EntityRef;
 
-    /// An opaque reference to an extended basic block in a function.
+    /// An opaque reference to a basic block in a function.
     #[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-    pub struct Ebb(u32);
-    entity_impl!(Ebb, "ebb");
+    pub struct Block(u32);
+    entity_impl!(Block, "block");
 
     #[test]
     fn comparator() {
-        let ebb1 = Ebb::new(1);
-        let ebb2 = Ebb::new(2);
-        let ebb3 = Ebb::new(3);
-        let ebb4 = Ebb::new(4);
-        let vals = [ebb1, ebb2, ebb4];
+        let block1 = Block::new(1);
+        let block2 = Block::new(2);
+        let block3 = Block::new(3);
+        let block4 = Block::new(4);
+        let vals = [block1, block2, block4];
         let comp = ();
-        assert_eq!(comp.search(ebb1, &vals), Ok(0));
-        assert_eq!(comp.search(ebb3, &vals), Err(2));
-        assert_eq!(comp.search(ebb4, &vals), Ok(2));
+        assert_eq!(comp.search(block1, &vals), Ok(0));
+        assert_eq!(comp.search(block3, &vals), Err(2));
+        assert_eq!(comp.search(block4, &vals), Ok(2));
     }
 
     #[test]