pgsql: ci: Move execution method of tasks into yaml templates

ci: Move execution method of tasks into yaml templates

This is done in preparation for making the compute resources for CI
configurable. It also looks cleaner.

Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/20230808021541.7lbzdefvma7qmn3w@awork3.anarazel.de
Backpatch: 15-, where CI support was added

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/462f4df0a86d2c497a1739f386835d246ea8645e

Modified Files
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.cirrus.yml | 77 +++++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 55 insertions(+), 22 deletions(-)