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outdated comment was also fixed.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/codegen/src/isa/constraints.rs

@@ -95,7 +95,7 @@ pub struct RecipeConstraints {
     /// If the instruction takes a variable number of operands, the register constraints for those
     /// operands must be computed dynamically.
     ///
-    /// - For branches and jumps, EBB arguments must match the expectations of the destination EBB.
+    /// - For branches and jumps, block arguments must match the expectations of the destination block.
     /// - For calls and returns, the calling convention ABI specifies constraints.
     pub ins: &'static [OperandConstraint],
 
@@ -173,7 +173,7 @@ pub struct BranchRange {
 impl BranchRange {
     /// Determine if this branch range can represent the range from `branch` to `dest`, where
     /// `branch` is the code offset of the branch instruction itself and `dest` is the code offset
-    /// of the destination EBB header.
+    /// of the destination block header.
     ///
     /// This method does not detect if the range is larger than 2 GB.
     pub fn contains(self, branch: CodeOffset, dest: CodeOffset) -> bool {