feat(alert): add ability to use alert inline

[amandaejohnston]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Alert can only be presented through alertController.

Issue URL: N/A

What is the new behavior?

• Alert can now be used as an inline component, with support for both isOpen and trigger.
• The .ion-delegate-host wrapper element for inline overlays is now only added for ion-modal and ion-popover, in order to fix an issue where the alert would appear underneath the backdrop.

Does this introduce a breaking change?

• Yes
• No

Other information

Dev build: 6.3.7-dev.11668790733.16ac6270

[liamdebeasi]

The position: relative change is concerning, but it looks like this is due to the ion-delegate-host bug. Once that is resolved we should be able to remove position: relative. Looks great otherwise!

[liamdebeasi]

Great job!

[amandaejohnston]

After talking on Slack, I've patched the ion-delegate-host element to only be added for modals and popovers, and reverted the patches to the alert CSS and a11y test. I also added a dev build to the bottom of the PR description. 👍