[clang] [Serialization] Check for stack exhaustion when reading declarations (PR #79875)

[David Blaikie via cfe-commits]

dwblaikie wrote:

there's a couple of tests that use `ulimit` (`clang/test/SemaCXX/PR51712-large-array-constexpr-check-oom.cpp` and `clang/test/PCH/leakfiles.test`) - so that technique could be used to test this in a way that's fast enough to check in?

https://github.com/llvm/llvm-project/pull/79875