All fields should have ARIA label overrides

[BenHenning]

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Problem

Without context there's not really any indication as to what the value means for a particular field when using a screen reader.

Request

In order to ensure that block and field readouts provide sufficient context, all built-in shadow block and field input cases should have contextual overrides (like the math arithmetic block).

Alternatives considered

No response

Additional context

No response

[microbit-robert]

If it's useful, these are the changes I made for user testing. Most are not controversial.

The things of note are that:

• we dropped 'arithmetic' considering the reading age of our target audience
• we dropped the preceding "Variable" text from the variable readout. The ariaName change resulted in "Variable, [variableName], variable" which was a bit excessive. You could jump one way or the other on this, e.g., "Variable, [variableName]" or "[variableName], variable". We have the latter just for consistency with the label order for other fields.

This is not an extensive review of blocks, just things we bumped up against when reviewing screen reader output in MakeCode.