[DebugInfo] Use SplitTemplateClosers (foo<bar<baz> >) in DWARF too

Summary:
D76801 caused some regressions in debuginfo compatibility by changing how
certain functions were named.

For CodeView we try to mirror MSVC exactly: this was fixed in a549c0d0
For DWARF the situation is murkier. Per David Blaikie:
> In general DWARF doesn't specify this at all.
> [...]
> This isn't the only naming divergence between GCC and Clang

Nevertheless, including the space seems to provide better compatibility with
GCC and GDB. E.g. cpexprs.cc in the GDB testsuite requires this formatting.
And there was no particular desire to change the printing of names in debug
info in the first place (just in diagnostics and other more user-facing text).

Fixes PR46052

Reviewers: dblaikie, labath

Subscribers: aprantl, cfe-commits, dyung

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80554