Fix extra numbers showing up when enabling VoiceControl (#163593)

Fixes https://github.com/flutter/flutter/issues/158477 and
https://github.com/flutter/flutter/issues/156368.

The excess numbers in both PRs are caused by all `SemanticObjects`
returning `YES` for `accessibilityRespondsToUserInteraction`, even if it
has no semantic actions. For example, a SemanticObject with just a label
has semantic information (the label) but no action. This PR adds a
check, ensuring that an `SemanticObjects` has at least one accessible
action before returning `YES`

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.