[CIR] Add array new cookie support (#163649)
This patch adds the minimal support for array cookies needed to enable
ClangIR generation for an array new expression that requires cookies but
does not require an explicit initializer.
This only provides the cookie support for the base Itanium CXXABI.
Different cookie calculations are required for AppleARM64, which will be
added in a subsequent patch.
Ported from ClangIR incubator PR
https://github.com/llvm/clangir/pull/1297.
This is the second PR in a series intended to address
https://github.com/llvm/llvm-project/issues/160383.
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Co-authored-by: Andy Kaylor <akaylor@nvidia.com>
