[llvm-opt-report] Left justify unrolling counts, etc.

In the left part of the reports, we have things like U<number>; if some of
these numbers use more digits than others, we don't want a space in between the
U and the start of the number. Instead, the space should come afterward. This
way it is clear that the number goes with the U and not any other optimization
indicator that might come later on the line.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283518 91177308-0d34-0410-b5e6-96231b3b80d8

test/tools/llvm-opt-report/Inputs/unrl.c

@@ -0,0 +1,10 @@
+void bar();
+
+void foo() {
+  for (int i = 0; i < 5; ++i)
+    bar();
+
+  for (int i = 0; i < 11; ++i)
+    bar();
+}
+

test/tools/llvm-opt-report/Inputs/unrl.yaml

@@ -0,0 +1,42 @@
+--- !Missed
+Pass:            inline
+Name:            NoDefinition
+DebugLoc:        { File: Inputs/unrl.c, Line: 5, Column: 5 }
+Function:        foo
+Args:            
+  - Callee:          bar
+  - String:          ' will not be inlined into '
+  - Caller:          foo
+  - String:          ' because its definition is unavailable'
+...
+--- !Missed
+Pass:            inline
+Name:            NoDefinition
+DebugLoc:        { File: Inputs/unrl.c, Line: 8, Column: 5 }
+Function:        foo
+Args:            
+  - Callee:          bar
+  - String:          ' will not be inlined into '
+  - Caller:          foo
+  - String:          ' because its definition is unavailable'
+...
+--- !Passed
+Pass:            loop-unroll
+Name:            FullyUnrolled
+DebugLoc:        { File: Inputs/unrl.c, Line: 7, Column: 3 }
+Function:        foo
+Args:            
+  - String:          'completely unrolled loop with '
+  - UnrollCount:     '11'
+  - String:          ' iterations'
+...
+--- !Passed
+Pass:            loop-unroll
+Name:            FullyUnrolled
+DebugLoc:        { File: Inputs/unrl.c, Line: 4, Column: 3 }
+Function:        foo
+Args:            
+  - String:          'completely unrolled loop with '
+  - UnrollCount:     '5'
+  - String:          ' iterations'
+...

test/tools/llvm-opt-report/unrl.test

@@ -0,0 +1,14 @@
+RUN: llvm-opt-report -r %p %p/Inputs/unrl.yaml | FileCheck -strict-whitespace %s
+
+; CHECK: < {{.*[/\]}}unrl.c
+; CHECK-NEXT:  1          | void bar();
+; CHECK-NEXT:  2          | 
+; CHECK-NEXT:  3          | void foo() {
+; CHECK-NEXT:  4  U5      |   for (int i = 0; i < 5; ++i)
+; CHECK-NEXT:  5          |     bar();
+; CHECK-NEXT:  6          | 
+; CHECK-NEXT:  7  U11     |   for (int i = 0; i < 11; ++i)
+; CHECK-NEXT:  8          |     bar();
+; CHECK-NEXT:  9          | }
+; CHECK-NEXT: 10          | 
+