Incorrect aria-posinset for Pickers with Sections

### Provide a general summary of the issue here

Looking at https://react-spectrum.adobe.com/Picker#sections the first element in the popup (Chocolate) has an aria-posinset of 2 although it is the first option.

### 🤔 Expected Behavior?

One would expect that
- the **Choclate** in **Neopolitan flavors** group has `aria-posinset=1`
- the **Matcha** in the **Others** group has `aria-posinset=4` because the aria-setsize is 6, if posinset should restart in each section the aria-setsize should be 3 and not 6

I looked at my Spectrum v1 app and there the pos computation is correct so this looks like a regression in v2

### 😯 Current Behavior

Numbering starts with 2 and restarts in each group which does not match with the aria-setsize

### 💁 Possible Solution

_No response_

### 🔦 Context

_No response_

### 🖥️ Steps to Reproduce

Open the sample at https://react-spectrum.adobe.com/Picker#sections and inspect the DOM once you opened the Picker

### Version

v1.0.0 (or what is used on the docs page)

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

Chrome

### If other, please specify.

_No response_

### What operating system are you using?

OS-X

### 🧢 Your Company/Team

_No response_

### 🕷 Tracking Issue

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