[CP][stable channel] Merge a3767f7db86a85fcd6201e9357ad47b884002b66 to stable channel (2.13)

[a-siva]

commit(s) to merge: a3767f7

merge instructions: clean merge

What is the issue: Flutter AOT precompiler crashes (flutter/flutter#83094)

What is the fix: Generate non-speculative Unbox instructions for Phis

Why cherrypick: This crash was reported by a Flutter user and it is possible other Flutter users may also run into this crash. When such a crash is reported it is not obvious the crash is because of this issue and we would spend additional engineering cycles investigating the crash and narrow it down to this cause.

Risk: The change has landed in master and is in the process of being rolled into Flutter. We should wait for it to be rolled fully which I hope will happen over the weekend.

Link to original issue(s): flutter/flutter#83094

/cc @kevmoo @mit-mit @whesse @athomas @vsmenon @franklinyow @alexmarkov

[franklinyow]

CC @kf6gpe

[franklinyow]

@alexmarkov @mraleph
The original issue flutter/flutter#83094 is still open.
Can you give an update on the roll progress?

[kf6gpe]

I don't think this made the last cherrypick window. @christopherfujino can you confirm?

If not, let's keep this in mind for the next hotfix release. There's not one scheduled, but I could see taking this if we get enough to proceed.

[franklinyow]

@kf6gpe We have not approved this pick. So this won't be in the last cherrypick window.

[kf6gpe]

Got it. I'll wait until it's approved and then add it to the list. Thanks!

[franklinyow]

Description:
Fix an crashing issue in Flutter precompiler , see flutter/flutter#83094 for detail

[athomas]

Merged to stable in 516eb3b (2.13.3).