Revert "[ffi] Remove deprecated Pointer.elementAt"
This reverts commit 789302053e.
Reason for revert: This breaks flutter engine
```
../../../../../../../.pub-cache/hosted/pub.dev/posix-6.0.1/lib/src/util/conversions.dart:32:32: Error: The method 'elementAt' isn't defined for the class 'Pointer<Pointer<Int8>>'.
- 'Pointer' is from 'dart:ffi'.
- 'Int8' is from 'dart:ffi'.
Try correcting the name to the name of an existing method, or defining a method named 'elementAt'.
final _value = cStringList.elementAt(count).value;
```
```
ui 0.0.0
├── archive 4.0.3
│ ├── posix 6.0.1
│ │ ├── ffi 2.1.4
│ │ ├── meta...
│ │ └── path...
```
Reverting while we remove uses upstream.
https://github.com/onepub-dev/dart_posix/pull/17
Original change's description:
> [ffi] Remove deprecated `Pointer.elementAt`
>
> Bug: https://github.com/dart-lang/sdk/issues/54250
>
> TEST=tests/ffi
>
> CoreLibraryReviewExempt: Removing deprecated member after 1+ year.
> Change-Id: I2234f28126e0788860a54cbe6aa82bc76b49c8d8
> Cq-Include-Trybots: dart/try:vm-aot-android-release-arm64c-try,vm-aot-android-release-arm_x64-try,vm-aot-asan-linux-release-x64-try,vm-aot-linux-debug-x64-try,vm-aot-linux-debug-x64c-try,vm-aot-mac-release-arm64-try,vm-aot-msan-linux-release-x64-try,vm-aot-obfuscate-linux-release-x64-try,vm-aot-optimization-level-linux-release-x64-try,vm-aot-tsan-linux-release-x64-try,vm-aot-ubsan-linux-release-x64-try,vm-aot-win-debug-x64-try,vm-aot-win-debug-x64c-try,vm-appjit-linux-debug-x64-try,vm-asan-linux-release-arm64-try,vm-asan-linux-release-x64-try,vm-checked-mac-release-arm64-try,vm-eager-optimization-linux-release-ia32-try,vm-eager-optimization-linux-release-x64-try,vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64c-try,vm-ffi-mac-debug-simarm64_arm64-try,vm-ffi-qemu-linux-release-arm-try,vm-ffi-qemu-linux-release-riscv64-try,vm-fuchsia-release-x64-try,vm-linux-debug-ia32-try,vm-linux-debug-x64-try,vm-linux-debug-x64c-try,vm-mac-debug-arm64-try,vm-mac-debug-x64-try,vm-msan-linux-release-arm64-try,vm-msan-linux-release-x64-try,vm-reload-linux-debug-x64-try,vm-reload-rollback-linux-debug-x64-try,vm-tsan-linux-release-arm64-try,vm-tsan-linux-release-x64-try,vm-ubsan-linux-release-arm64-try,vm-ubsan-linux-release-x64-try,vm-win-debug-x64-try,vm-win-debug-x64c-try,vm-win-release-ia32-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/421740
> Reviewed-by: Hossein Yousefi <yousefi@google.com>
> Commit-Queue: Daco Harkes <dacoharkes@google.com>
Bug: https://github.com/dart-lang/sdk/issues/54250
Cq-Include-Trybots: dart/try:vm-aot-android-release-arm64c-try,vm-aot-android-release-arm_x64-try,vm-aot-asan-linux-release-x64-try,vm-aot-linux-debug-x64-try,vm-aot-linux-debug-x64c-try,vm-aot-mac-release-arm64-try,vm-aot-msan-linux-release-x64-try,vm-aot-obfuscate-linux-release-x64-try,vm-aot-optimization-level-linux-release-x64-try,vm-aot-tsan-linux-release-x64-try,vm-aot-ubsan-linux-release-x64-try,vm-aot-win-debug-x64-try,vm-aot-win-debug-x64c-try,vm-appjit-linux-debug-x64-try,vm-asan-linux-release-arm64-try,vm-asan-linux-release-x64-try,vm-checked-mac-release-arm64-try,vm-eager-optimization-linux-release-ia32-try,vm-eager-optimization-linux-release-x64-try,vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64c-try,vm-ffi-mac-debug-simarm64_arm64-try,vm-ffi-qemu-linux-release-arm-try,vm-ffi-qemu-linux-release-riscv64-try,vm-fuchsia-release-x64-try,vm-linux-debug-ia32-try,vm-linux-debug-x64-try,vm-linux-debug-x64c-try,vm-mac-debug-arm64-try,vm-mac-debug-x64-try,vm-msan-linux-release-arm64-try,vm-msan-linux-release-x64-try,vm-reload-linux-debug-x64-try,vm-reload-rollback-linux-debug-x64-try,vm-tsan-linux-release-arm64-try,vm-tsan-linux-release-x64-try,vm-ubsan-linux-release-arm64-try,vm-ubsan-linux-release-x64-try,vm-win-debug-x64-try,vm-win-debug-x64c-try,vm-win-release-ia32-try
Change-Id: I9cd3d4800840bf28182225824b82c469eb957087
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/422460
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Nate Biggs <natebiggs@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Daco Harkes
7427e655f6