[Bug]: Overlay popovers have incorrect tip placement in RTL

### Code of conduct

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

### Impacted component(s)

sp-overlay, sp-popover

### Expected behavior

Popover tip should align with the trigger like in LTR: https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/overlay--default&globals=system:express

### Actual behavior

https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/overlay--default&globals=system:express;textDirection:rtl

### Screenshots

_No response_

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

_No response_

### How can we reproduce this issue?

1. Go to https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/overlay--default&globals=system:express;textDirection:rtl
2. Open the popover

### 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!

Open the linked Storybook overlay example in RTL and compare it with the LTR version first. Then inspect the sp-overlay and sp-popover components to trace tip placement; done means the popover tip aligns with its trigger in RTL as it does in LTR.

Written by the indexing model from the issue text.