[LifetimeSafety] Add missing origins stats for lifetime analysis  (#166568)

This PR adds the implementation for printing missing origin stats for
lifetime analysis.

**Purpose:**

This capability is added to track the expression types with missing
origin. While retrieving the origins from origin manager, some
expressions show missing origins. Currently these are created on the fly
using getOrCreate function. For analysing the coverage of the check, it
will be necessary to see what kind of expressions have a missing origin.
It prints the counts in this form: `QualType : count` and `StmtClassName
: count`.

**Approach:**

1. The signature of the runLifetimeAnalysis function is changed to
return the LifetimeAnalysis object which will be used to get the origin
manager which can be used for finding the count of missing origins.
2. The count of missing origins is kept in origin manager while the CFG
is visited as part of the analysis.

Example output:

For the file llvm-project/llvm/lib/Demangle/Demangle.cpp:

```
*** LifetimeSafety Missing Origin per QualType: (QualType : count) :

value_type : 1
char * : 3


*** LifetimeSafety Missing Origin per StmtClassName: (StmtClassName : count) :

BinaryOperator : 3
UnaryOperator : 1

Total missing origins: 4
```