Enforce asterisk alignment for C++ and ObjC pointers

[stuartmorgan-g]

So far we've been using the default mode of prevailing-in-file, which
means we aren't consistent within each language what mode we use. Now
that clang-format can identify ObjC headers (which didn't used to be the
case), we can enforce different styles for the two languages.

This sets left-aligned for C++ to match the Flutter engine, and
right-aligned for ObjC to match the prevaling Apple style.

No version change: automated whitespace-only change with no actual effect on clients.

No CHANGELOG change: uninteresting mechanical change.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

[stuartmorgan-g]

@jmagman A lot more ObjC code here was using left-aligned than I expected. I assumed we'd want to follow Apple's usual style, but we could also use left-aligned for everything (or as I like to think of it "correct" 😁 ); I leave it entirely up to you.

[gaaclarke]

FWIW the google style guides for objc and c++ are agnostic to the placement of the asterisks.

[stuartmorgan-g]

FWIW the google style guides for objc and c++ are agnostic to the placement of the asterisks.

Google style is agnostic, but I've never been on a team that doesn't have a team-level convention for this in order to have local consistency.

[gaaclarke]

sgtm, whatever you all want to do. I renamed the PR since it sounded very scary, potentially having to do with memory alignment instead of code formatting =)

[stuartmorgan-g]

🤷🏻 "pointer alignment" is the name of the clang-format setting.

[gaaclarke]

In the context of formatting code "pointer alignment" makes sense in the context of making changes to a codebase it is ambiguous and scary. I imaging someone investigating a mysterious crash and that PR title jumping out at them.

[jmagman]

@jmagman A lot more ObjC code here was using left-aligned than I expected. I assumed we'd want to follow Apple's usual style, but we could also use left-aligned for everything (or as I like to think of it "correct" 😁 ); I leave it entirely up to you.

Let's keep right-alignment to match the Apple style. As long as it's consistent, and better if a formatter can fix it for me, I can live with either.

LGTM