Replace AppIntro by Compose Pager

[ArnyminerZ]

The PR should be in Draft state during development. As soon as it's finished, it should be marked as Ready for review and a reviewer should be chosen.

See also: Writing A Great Pull Request Description

Purpose

Migrates all AppIntro code to Compose Pager.

Short description

• Added ButtonWithIcon which is a circular button with an icon inside.
• Added PositionIndicator which shows multiple circles indicating the current position of the slider.
• Added IntroScreen which handles all the things AppIntro did before.
• Got rid of AppIntro dependency

Checklist

• The PR has a proper title, description and label.
• I have self-reviewed the PR.
• I have added documentation to complex functions and functions that can be used by other modules.
• I have added reasonable tests or consciously decided to not add tests.

[mbiebl]

Would probably be a good idea to mention in the git log message why AppIntro was replaced/removed.

Two smaller issues:

• fails to build as the code still references appintro:

$ grep appintro app/src/ -R
app/src/main/kotlin/at/bitfire/davdroid/ui/intro/WelcomePage.kt:                            com.github.appintro.R.dimen.appintro2_bottombar_height
app/src/main/kotlin/at/bitfire/davdroid/ui/intro/WelcomePage.kt:                            com.github.appintro.R.dimen.appintro2_bottombar_height

• Small typo in the commit message: "Migrated into to compose". This probably should read "Migrated Intro to compose"

[sunkup]

@ArnyminerZ Please request a review from me again when ready :)

[ArnyminerZ]

Should be

[sunkup]

Looking good. Minor comments :)

[rfc2822]

Looking forward to remove the last non-Compose code :) Noticed some things:

1. When you click through the pages (for instance, only 2 pages like in the video), DAVx5 quits instead of going to the Accounts overview:

Screen_recording_20240623_105103.webm

2. I think it would look better if the position indicator circles would always have the same distance to each other.

Old app intro:

In contrast, the new app intro with the big distance between the circles:

I think we should define a fixed dp distance between the circles.

3. I'd leave ButtonWithIcon and PositionIndicator in the screen where it's needed. We don't need it somewhere else and it makes the composable list long and at some time confusing. When we at some time need it somewhere else, we can extract it to the composables package.