feat(angular, react, vue): add support for autoMountComponent

[liamdebeasi]

Docs: ionic-team/ionic-docs#2432

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?

Issue URL: Internal ticket.

What is the new behavior?

• Adds the ability to have inline modals and popovers automatically mount their inner contents on creation. The contents will only be unmounted when the parent modal/popover is unmounted. Re-mounting the inner modal/popover does not preserve the inner content state.

Does this introduce a breaking change?

• Yes
• No

Other information

[liamdebeasi]

Bikeshedding a bit... I'm not a huge fan of autoMountComponent. Some alternatives:

• keepMounted
• autoMount
• keepComponentMounted

Anyone have a preference? keepMounted is what MUI calls it (https://mui.com/material-ui/react-modal/#performance), but I worry that it implies that we will keep ion-modal mounted.

---

I added reviewers to get feedback on the prop name. The code itself is the same code that was already reviewed.

[amandaejohnston]

Maybe keepContentsMounted? It's similar to the existing keepMounted API, but it makes it more clear what exactly we're mounting.

[sean-perkins]

Minor suggestions. Unsure how much of the language should be around the prop name vs. the behavior of the feature. I do not have any strong opinions on either.