Add sub roles to MacOS adapter

[HolgerGottChristensen]

Adds initial support for accessibility sub roles to the MacOS adapter, allowing AccessKit to expose Toggle buttons, Switch and more, correctly to VoiceOver.

Needed clarifications:

• Does AccessKit handle math, and all the math roles from chromium? (Not currently available in AccessKit)
• How are search boxes represented? Role from MacOS Multiple roles from chromium (Role::SearchInput)
• How are secure textfields represented? Role from MacOS (Role::PasswordInput)

Fixes #477

Fixes #372

[DataTriny]

Does AccessKit handle math, and all the math roles from chromium?

We do have these roles and I think they are all named exactly like Chromium's. Please add them if possible.

How is search box represented?

By giving Role::SearchInput to a node.

How is secure textfields represented?

By giving Role::PasswordInput to a node.

[HolgerGottChristensen]

I dont see any of the math roles in the list of roles: https://github.com/AccessKit/accesskit/blob/main/common/src/lib.rs#L55

Are they defined somewhere else?

[DataTriny]

Woops, sorry. We must have removed them at some point. Please do the same.

[DataTriny]

With the changes from this PR, tabs are correctly announced as tabs by VoiceOver. This can be tested by running the gallery example from my fork of Slint. I've updated the PR description accordingly.

[mwcampbell]

I don't recall dropping math roles. It's more likely that when I copied the roles from Chromium in July 2021, those roles didn't exist yet.

[HolgerGottChristensen]

I don't recall dropping math roles. It's more likely that when I copied the roles from Chromium in July 2021, those roles didn't exist yet.

Yes, they were added in October 2021, so right after you copied the roles :)
chromium/chromium@6ee9585

[DataTriny]

Thank you @HolgerGottChristensen!