[flang] crash at Fortran::semantics::ScopeHandler::SayDerivedType

https://godbolt.org/z/no39zTsvs

The following code:

```fortran
module m1
type pair
end type
interface pair

subroutine s(var)

end subroutine s
!RUN: %python %S/test_errors.py %s %flang_fc1
module procedure f
end interface

end
module m2
type pair
end type
end
module REALVAR7
type pair
end type
end
program main
use m1
use m2
use m3
!ERROR: Reference to 'pair' is ambiguous
type(pair) error
end
```

Resulted in this output:
```
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and instructions to reproduce the bug.
Stack dump:
0. Program arguments: /cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang -fc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelocation-model pic -pic-level 2 -pic-is-pie -target-cpu x86-64 -debug-info-kind=standalone -resource-dir /cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/lib/clang/23 -fintrinsic-modules-path /cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/lib/clang/23/finclude/flang/x86_64-unknown-linux-gnu -mframe-pointer=all -o /tmp/example-e6e977.o -x f95 /app/example.f90
#0 0x0000000004b89cc8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4b89cc8)
#1 0x0000000004b86e04 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#2 0x00007ce936245330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#3 0x00000000057492b4 Fortran::semantics::ScopeHandler::SayDerivedType(Fortran::parser::CharBlock const&, Fortran::parser::MessageFixedText&&, Fortran::semantics::Scope const&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x57492b4)
#4 0x000000000575024c Fortran::semantics::InterfaceVisitor::CheckGenericProcedures(Fortran::semantics::Symbol&) (.part.0) resolve-names.cpp:0:0
#5 0x0000000005788933 Fortran::semantics::ResolveNamesVisitor::FinishSpecificationPart(std::__cxx11::list> const&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x5788933)
#6 0x00000000057becf3 Fortran::semantics::ResolveNamesVisitor::Pre(Fortran::parser::SpecificationPart const&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x57becf3)
#7 0x00000000057cab97 Fortran::semantics::ResolveNamesVisitor::ResolveSpecificationParts(Fortran::semantics::ProgramTree&) (.part.0) resolve-names.cpp:0:0
#8 0x00000000057d84d3 Fortran::semantics::ResolveNamesVisitor::Pre(Fortran::parser::ProgramUnit const&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x57d84d3)
#9 0x00000000057d9b64 Fortran::semantics::ResolveNames(Fortran::semantics::SemanticsContext&, Fortran::parser::Program const&, Fortran::semantics::Scope&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x57d9b64)
#10 0x0000000005869440 Fortran::semantics::Semantics::Perform() (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x5869440)
#11 0x0000000004bef318 Fortran::frontend::FrontendAction::runSemanticChecks() (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4bef318)
#12 0x0000000004ed9f40 Fortran::frontend::CodeGenAction::beginSourceFileAction() (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4ed9f40)
#13 0x0000000004bedf75 Fortran::frontend::FrontendAction::beginSourceFile(Fortran::frontend::CompilerInstance&, Fortran::frontend::FrontendInputFile const&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4bedf75)
#14 0x0000000004bdb16f Fortran::frontend::CompilerInstance::executeAction(Fortran::frontend::FrontendAction&) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4bdb16f)
#15 0x0000000004bf9b1f Fortran::frontend::executeCompilerInvocation(Fortran::frontend::CompilerInstance*) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x4bf9b1f)
#16 0x0000000002e8be05 fc1_main(llvm::ArrayRef, char const*) (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x2e8be05)
#17 0x0000000002d85f79 main (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x2d85f79)
#18 0x00007ce93622a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
#19 0x00007ce93622a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
#20 0x0000000002e8a6d5 _start (/cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin/flang+0x2e8a6d5)
flang-23: error: unable to execute command: Segmentation fault (core dumped)
flang-23: error: flang frontend command failed with exit code -2 (use -v to see invocation)
flang version 23.0.0git (https://github.com/llvm/llvm-project.git 8d61da2569a975346150371cb0d317fb9339be0c)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /cefs/de/de160e63334011ce09fe1629_clang-llvmflang-trunk-20260616/bin
flang-23: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING CRASH REPRODUCER FILES TO THE BUG REPORT:
flang-23: note: diagnostic msg: /tmp/example-87cd6f
flang-23: note: diagnostic msg: /tmp/example-87cd6f.sh
flang-23: note: diagnostic msg:

********************
```

To reproduce:
```
flang ./test.f90
```

Compiler version:
```
Ubuntu flang version 22.1.8 (++20260613092238+e80beda6e255-1~exp1~20260613092253.78)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-22/bin
```

*This bug was found by [fusion-fuzz](https://github.com/fusion-fuzz/fusion-fuzz)*

Reproduce the crash with the provided test.f90 example using flang, then inspect Fortran::semantics::ScopeHandler::SayDerivedType and InterfaceVisitor::CheckGenericProcedures in resolve-names.cpp. Use the test_errors.py framework mentioned in the reproducer to add coverage; done means the ambiguous reference produces a diagnostic instead of a segmentation fault.

Written by the indexing model from the issue text.