chores: set up `nix-github-actions` #3215

Job	Run time
nix-matrix	22s
pg_regress (x86_64-linux)	45s
packer (x86_64-linux)	1m 15s
psql_15 (x86_64-linux)	1m 20s
dbmate-tool (x86_64-linux)	47s
pre-commit (x86_64-linux)	46s
wrappers (x86_64-linux)	58s
wal-g-2 (x86_64-linux)	42s
psql_17 (x86_64-linux)	1m 23s
treefmt (x86_64-linux)	47s
wal-g-3 (x86_64-linux)	48s
psql_orioledb-17 (x86_64-linux)	1m 17s
devShell (x86_64-linux)	2m 9s
run-testinfra / prepare	42s
run-tests / prepare	42s
run-testinfra / test-ami-nix ("17")	41m 42s
run-testinfra / test-ami-nix ("15")	43m 13s
run-testinfra / test-ami-nix ("orioledb-17")	41m 43s
run-tests / build ("17")	1m 34s
run-tests / build ("15")	1m 42s
run-tests / build ("orioledb-17")	1m 47s
	2h 26m 24s

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