refactor: rename dummy table id to tmp table id

[xxchan]

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What's changed and what's your intention?

I mistakenly thought "dummy" means placeholder. But it actually means a temporary id which will be replaced later. So I think "tmp" is a more proper name.

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[xxchan]

• #19509 : 2 dependent PRs (#18935 , #19510 ) 👈 (View in Graphite)
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