pgsql: Make more use of RELKIND_HAS_STORAGE()

Make more use of RELKIND_HAS_STORAGE()

Make use of RELKIND_HAS_STORAGE() where appropriate, instead of
listing out the relkinds individually. No behavior change intended.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: /messages/by-id/7a22bf51-2480-d999-1794-191ba67ff47c@2ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ffd2582297b86f640b60ba46097b70743f920d35

Modified Files
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src/backend/catalog/heap.c | 7 +---
src/backend/postmaster/pgstat.c | 6 +---
src/backend/utils/adt/dbsize.c | 73 ++++++++++++++++-------------------------
3 files changed, 31 insertions(+), 55 deletions(-)