[llvm] [memprof] Use std::move in toMemProfRecord (PR #93133)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> This leaves the current IndexedMemProfRecord in a bad state. How can we ensure that users don't accidentally try to read after this method has been called?
> 
> I'm also skeptical how much impact this has in real usage since we don't expect to read all records for a single module. Perhaps we can try safer optimizations such as reserve() for the AllocSites vector (and the Callsites vector too)?

`AI` here is a local variable.  This patch does not modify the current `IndexedMemProfRecord` in any way.  In fact, `toMemProfRecord` is a const function.

https://github.com/llvm/llvm-project/pull/93133