[DebugInfo] Fix container types failing to find template args

[Walnut356]

This is a less pervasive (but also less powerful) alternative to #144394.

This change only provides benefits to container types on MSVC. The TL;DR is that nodes that don't populate/aren't discoverable in the PDB for various reasons are given an alternate lookup path that generates the nodes by acquiring the base-type via some gross string manipulation and then asking clang for the node it wants (e.g. "ref$<i32>" -> "i32" -> target.FindFirstType("i32").GetPointerType() -> i32 *, which is a valid type for the container to use)

The before/afters are the same as in the above PR's *-msvc LLDB screenshots. This works as a stopgap while the above PR is evaluated, but I think that PR is still a much better solution.

[rustbot]

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