Add explanation of what "automatic" means in 2.2.2 and 1.4.2, cross-reference

[patrickhlauke]

Closes #2863

This is an alternative to #2906 which more directly addresses the definition, as well as providing further explanation/cross-linking for overlapping SCs:

• removes the mention of "audio" from the intent for 2.2.2 Pause, Stop, Hide, which is clearly aimed at visual content only
• adds a basic explanation of what's meant by "starts automatically" to 2.2.2
• adds relevant cross-references/overlaps to other SCs to 2.2.2
• adds a basic explanation of what's meant by "plays automatically" to 1.4.2 Audio Control
• adds a further clarification to 2.3.3 Animation from Interactions

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[patrickhlauke]

Noting here though that if the WG feels that "automatically" literally only refers to things happening on a timer, and not as the result of any interaction, then this PR would introduce a breaking change, so would need to be neutered/repointed - which could be done relatively straightforwardly here.

In short, the group needs to decide:

• is "automatic" anything where there is no expectation/intentionality on the part of the user - they haven't explicitly activated/clicked/pressed something (so this would include things that change unexpectedly, even on hover or scrolling...which yes would, at least for movement-based animations, essentially cover the same/similar ground as 2.3.3), or
• is "automatic" anything that happens fully divorced from a user interaction in general (meaning that things that happen on scrolling, hovering, focusing, blurring, etc would not be covered by 2.2.2 nor 1.4.2)

(in hindsight, it almost feels like 2.3.3 could have been unnecessary if "starts automatically" had actually been defined properly ... so here we're left trying to disentangle potential overlaps)

[mbgower]

Group to review independently before next meeting. MOving to 'ready for review"

[patrickhlauke]

Resolved conflict, will look at remaining open comments on this.