feat(Dialog): All variants use flex

[FlyersPh9]

Changes

• .iui-dialog has display: flex; & flex-direction: column; rather than the class modifiers.
• Removed max-height from .iui-dialog-content, added a max-height using dvh to .iui-dialog-default in response to feat(Dialog): All variants use flex #1269 (comment).

Closes #1268.

Testing

• Ran visual tests.
• Checked in to ensure overflow is working as expected in browser & iOS Simulator.

Docs

https://github.com/iTwin/iTwinUI/wiki/iTwinUI-react-v3-migration-guide#dialog--modal

[mayank99]

LGTM. Lets wait for pending v2 PRs to release (#1250) before merging this.

(Blocking accidental merge using "Request changes".)

[mayank99]

@FlyersPh9 I vaguely recall there were some hacks we needed to do because display: flex was not always present. Think you'll be able to dig through the history and find those?

Here's one I found: #1066 (comment)

We might want to make some changes in the dialog code now that we can assume display: flex is always present.

[FlyersPh9]

@FlyersPh9 I vaguely recall there were some hacks we needed to do because display: flex was not always present. Think you'll be able to dig through the history and find those?

Here's one I found: #1066 (comment)

We might want to make some changes in the dialog code now that we can assume display: flex is always present.

Done, added a bullet to the PR description with more deets.

[mayank99]

Now unblocked! Just make sure to update branch or run git merge origin/dev locally before merging.