[clang] [Serialization] [ASTWriter] Try to not record namespace as much as possible (PR #179178)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> Not exactly sure why we end up with so many files as most of them seem redundant

In my experience, generally, this relates to https://github.com/llvm/llvm-project/pull/186056, where it will only merge the table if the number of base tables are more than 4.

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Would you like to convert the reproducer into a lit test and commit it in tree directly? This is helpful for the stability in the long term. Or I'd like to make it myself.

https://github.com/llvm/llvm-project/pull/179178