[lldb] Exclude "resume partial" prefix from demangled display name

[kastiglione]

When generating a display name for async resume partial functions, use the top-level function name. This primary purpose of this change is to display frames in backtraces using the function names found in source code. This will match developer expectations.

For demonstration, instead of a backtrace like this:

asyncHelper() at main.swift:2
(1) await resume partial function for static Main.main() at main.swift:13

with this change the backtrace will be:

asyncHelper() at main.swift:2
static Main.main() at main.swift:13

Depends on swiftlang/swift#36978

(cherry picked from #2868)