fix(components): [dropdown] fix visible-change event delay trigger #8601

[shooterRao]

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🧪 Playground Preview: https://element-plus.run/?pr=8602
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[chenxch]

Good job.

[chenxch]

cc @element-plus/backers Need to double check if there are other effects.

[tolking]

It seems that this PR broke the original A11y.

Use the before-show will not move focus into content.

Need to handle focus in the show event to make sure the internal DOM has been generated.

[YunYouJun]

@shooterRao Can you work with @tolking to fix the problem?

[chenxch]

In fact, we should talk about handleShowTooltip split into handleBeforeShowTooltip, handleBeforeShowTooltip is responsible for emit visible-change.

[chenxch]

use before-show 、show、before-hide

[shooterRao]

ok, I will fix this problem tomorrow.😀 @tolking @YunYouJun @chenxch