fix(autocomplete): default dropdown to position bottom as default

[Splaktar]

PR Checklist

Please check that your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

• The fix for autocomplete: shows dropdown on top even when there is no room #10859 has caused issues with the autocomplete dropdowns defaulting to position="top" instead of bottom.
• In some edge cases, dropdowns may be misaligned with their autocomplete input.

Issue Number:
Fixes #11656. Relates to #10859, #11629, #11575.

What is the new behavior?

• clean up and simplify the calculations for determining if the dropdown should use top or bottom position.
• add a test
• fix horizontal alignment edge cases
• fix $mdUtil.getViewportTop to handle when body scrolling is disabled
  • this is the actual fix for autocomplete: shows dropdown on top even when there is no room #10859

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

You can test the original CodePen from #10859 with the changes from this PR plus some helpful console logging in this CodePen to get a better understanding of the updated algorithm.

@marosoft if you have some time, please take a look at this to check the functionality. Please ask questions about the code changes if you have any as well 😄

[Splaktar]

PR #11664 includes some similar (but different) changes related to part of this PR. It also includes some more unit tests. I need to take a look at it to see if I should modify the approach of this PR slightly.

[veneliniliev]

please merge this!

[Splaktar]

I looked at the test added in PR #11664, but unfortunately it passes without these changes (and without the changes in that PR) so it doesn't appear to provide any value to this PR.

I've rebased this PR and it should be ready for presubmit.