arrow

ARROW-10064: [C++] Resolve compile warnings on Apple Clang 12

```
../src/arrow/util/uri.cc:172:19: error: loop variable 'seg' of type 'const nonstd::sv_lite::basic_string_view<char, std::__1::char_traits<char> >' creates a copy from type 'const nonstd::sv_lite::basic_string_view<char, std::__1::char_traits<char> >' [-Werror,-Wrange-loop-analysis]
  for (const auto seg : segments) {
                  ^
../src/arrow/util/uri.cc:172:8: note: use reference type 'const nonstd::sv_lite::basic_string_view<char, std::__1::char_traits<char> > &' to prevent copying
  for (const auto seg : segments) {
       ^~~~~~~~~~~~~~~~
                  &
```

and

```
../src/arrow/ipc/metadata_internal.cc:1157:20: error: loop variable 'pair' is always a copy because the range of type 'const arrow::ipc::internal::KVVector' (aka 'const Vector<Offset<flatbuf::KeyValue> >') does not return a reference [-Werror,-Wrange-loo
p-analysis]
  for (const auto& pair : *fb_metadata) {
                   ^
../src/arrow/ipc/metadata_internal.cc:1157:8: note: use non-reference type 'const org::apache::arrow::flatbuf::KeyValue *'
  for (const auto& pair : *fb_metadata) {
       ^~~~~~~~~~~~~~~~~~
```

Closes #8239 from kszucs/ARROW-10064

Authored-by: Krisztián Szűcs <szucs.krisztian@gmail.com>
Signed-off-by: Uwe L. Korn <uwe.korn@quantco.com>