[clang] [NFC][analyzer] Eliminate SwitchNodeBuilder (PR #188096)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

Ok, I started a test run, although I'm very skeptical about its chances of finding anything relevant. (It wouldn't have found the logic issue I fixed because currently there is no checker that splits the state in a `BranchCondition` callback. In general, I suspect that the analyzer codebase is full of incorrect logic in unusual cases – e.g. posteriorly overconstrained states, block location contexts, tricky ObjC features, the infamous node reclamation etc.)

https://github.com/llvm/llvm-project/pull/188096