[llvm] [llvm] Support multiple save/restore points in mir (PR #119357)

[Elizaveta Noskova via llvm-commits]

================
@@ -86,8 +86,8 @@ frameInfo:
   hasMustTailInVarArgFunc: false
   hasTailCall:     false
   localFrameSize:  0
-  savePoint:       ''
-  restorePoint:    ''
+  savePoints:      []
----------------
enoskova-sc wrote:

Аddressed. Now MIR can be consumed both in singular:
` savePoint:    '%bb.1'`
 and plural:
```
savePoint:
    - point:           '%bb.1'
```
   formats.
But printed in only plural format.

https://github.com/llvm/llvm-project/pull/119357