[clang] [clang] remove IsDefaulted bit from TemplateArgument (PR #155120)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

As I explained in the commit message, this is not removing the feature.

The information about which arguments were defaulted was already available in the AST before this bit was added.

And the bit is not correct as I said, being part of the canonical type means that this information will be homed in to whatever just happened to be the first template specialization produced. The canonical type is shared between all the same-types, so this would have forced all of those types to present the same information.

This patch removes the bit and uses the as-written template argument list to derive it.

This patch doesn't touch LLDB. If LLDB uses this bit, then LLDB also needs to be updated in the same manner as we are updating DebugInfo here.

https://github.com/llvm/llvm-project/pull/155120