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outdated comment was also fixed.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/docs/callex.clif

@@ -3,14 +3,14 @@ test verifier
 function %gcd(i32 uext, i32 uext) -> i32 uext system_v {
     fn0 = %divmod(i32 uext, i32 uext) -> i32 uext, i32 uext
 
-ebb1(v0: i32, v1: i32):
-    brz v1, ebb3
-    jump ebb2
+block1(v0: i32, v1: i32):
+    brz v1, block3
+    jump block2
 
-ebb2:
+block2:
     v2, v3 = call fn0(v0, v1)
     return v2
 
-ebb3:
+block3:
     return v0
 }

cranelift/docs/example.clif

@@ -3,17 +3,17 @@ test verifier
 function %average(i32, i32) -> f32 system_v {
     ss0 = explicit_slot 8         ; Stack slot for ``sum``.
 
-ebb1(v0: i32, v1: i32):
+block1(v0: i32, v1: i32):
     v2 = f64const 0x0.0
     stack_store v2, ss0
-    brz v1, ebb5                  ; Handle count == 0.
-    jump ebb2
+    brz v1, block5                  ; Handle count == 0.
+    jump block2
 
-ebb2:
+block2:
     v3 = iconst.i32 0
-    jump ebb3(v3)
+    jump block3(v3)
 
-ebb3(v4: i32):
+block3(v4: i32):
     v5 = imul_imm v4, 4
     v6 = iadd v0, v5
     v7 = load.f32 v6              ; array[i]
@@ -23,17 +23,17 @@ ebb3(v4: i32):
     stack_store v10, ss0
     v11 = iadd_imm v4, 1
     v12 = icmp ult v11, v1
-    brnz v12, ebb3(v11)           ; Loop backedge.
-    jump ebb4
+    brnz v12, block3(v11)           ; Loop backedge.
+    jump block4
 
-ebb4:
+block4:
     v13 = stack_load.f64 ss0
     v14 = fcvt_from_uint.f64 v1
     v15 = fdiv v13, v14
     v16 = fdemote.f32 v15
     return v16
 
-ebb5:
+block5:
     v100 = f32const +NaN
     return v100
 }

cranelift/docs/heapex-dyn.clif

@@ -6,7 +6,7 @@ function %add_members(i32, i64 vmctx) -> f32 baldrdash_system_v {
     gv2 = load.i32 notrap aligned gv0+72
     heap0 = dynamic gv1, min 0x1000, bound gv2, offset_guard 0
 
-ebb0(v0: i32, v6: i64):
+block0(v0: i32, v6: i64):
     v1 = heap_addr.i64 heap0, v0, 20
     v2 = load.f32 v1+16
     v3 = heap_addr.i64 heap0, v0, 24

cranelift/docs/heapex-sm32.clif

@@ -5,7 +5,7 @@ function %add_members(i32, i32 vmctx) -> f32 baldrdash_system_v {
     gv1 = load.i32 notrap aligned gv0+64
     heap0 = static gv1, min 0x1000, bound 0x10_0000, offset_guard 0x1000
 
-ebb0(v0: i32, v5: i32):
+block0(v0: i32, v5: i32):
     v1 = heap_addr.i32 heap0, v0, 1
     v2 = load.f32 v1+16
     v3 = load.f32 v1+20

cranelift/docs/heapex-sm64.clif

@@ -5,7 +5,7 @@ function %add_members(i32, i64 vmctx) -> f32 baldrdash_system_v {
     gv1 = load.i64 notrap aligned gv0+64
     heap0 = static gv1, min 0x1000, bound 0x1_0000_0000, offset_guard 0x8000_0000
 
-ebb0(v0: i32, v5: i64):
+block0(v0: i32, v5: i64):
     v1 = heap_addr.i64 heap0, v0, 1
     v2 = load.f32 v1+16
     v3 = load.f32 v1+20