Bug - NumberInput: values/validation status not announced to assistive tech on update

[thatblindgeye]

Describe the problem
Followup to #7806. Relevant comment chains: #7806 (review), #7806 (review), and #7806 (comment)

How do you reproduce the problem?

1. Go to Number input
2. Turn on VoiceOver or another screen reader
3. Use keyboard to update the input (either via the +/- buttons or within the input itself)
4. Notice the value does not get announced
   • In Chromium browsers, updating via buttons or via the input itself does not trigger an announcement. In Firefox and Safari, updating via the input announces the new value but updating via the buttons does not.

Expected behavior
The new value of the input and/or the validation status is announced to assistive tech

Is this issue blocking you?
N/A

Screenshots
N/A

What is your environment?
N/A

What is your product and what release date are you targeting?
N/A

Any other information?
N/A