[Bug]: ActionMenu placement="bottom-start" not working when in overlay + modal

### Code of conduct

- [x] I agree to follow this project's code of conduct.

### Impacted component(s)

sp-action-menu, sp-overlay, sp-dialog

### Library version

1.11.2

### Expected behavior

When sp-action-menu is used in a sp-dialog with sp-overlay, the `placement="bottom-start"` does not work.

### Actual behavior

Menu opens as if placement is `top`, `top-start`.

### Screenshots

_No response_

### What browsers are you seeing the problem in?

_No response_

### How can we reproduce this issue?

1. Go to '...'
2. Click on '....'
3. Scroll to '....'
4. Check console
5. See error

### Sample code or abstract reproduction which illustrates the problem

_No response_

### Severity

None

### Logs taken while reproducing problem

_No response_

### Would you like to track this issue in Jira?

- [x] Yes, please tell me the ticket number!

Start by reproducing the issue with sp-action-menu inside sp-dialog and sp-overlay using placement="bottom-start". Compare the resulting position with the expected bottom-start placement; done means the menu opens in the requested position in this overlay and modal combination.

Written by the indexing model from the issue text.