Speed up ./scripts/regenerate-schema

What does this MR do and why?

This MR implements this suggestion from @splattael to speed up ./scripts/regenerate-schema

Note: This MR targets Fix regenerate-schema for partitioned tables (!145132 - merged) so that we can merge these sequentially

Benchmark

$ hyperfine -w 1 "git checkout master && ./scripts/regenerate-schema" "git checkout speed-up-regenerate-schema && ./scripts/regenerate-schema"
Benchmark 1: git checkout master && ./scripts/regenerate-schema
  Time (mean ± σ):     63.146 s ±  3.044 s    [User: 22.405 s, System: 17.385 s]
  Range (min … max):   59.188 s … 68.509 s    10 runs

Benchmark 2: git checkout speed-up-regenerate-schema && ./scripts/regenerate-schema
  Time (mean ± σ):     41.531 s ±  2.692 s    [User: 10.148 s, System: 8.280 s]
  Range (min … max):   37.864 s … 47.741 s    10 runs

Summary
  git checkout speed-up-regenerate-schema && ./scripts/regenerate-schema ran
    1.52 ± 0.12 times faster than git checkout master && ./scripts/regenerate-schema

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