More future proof, better for self-hosted runners.

Example run times before:

       4s       CI completion
   2m 36s       Check we can downgrade the node (compile-gcc, sqlite3, liquid-regtest)
   2m 52s       Check we can downgrade the node (compile-gcc, postgres, regtest)
   3m 20s       Check we can downgrade the node (compile-gcc, sqlite3, regtest, 1)
   3m 20s       Check we can downgrade the node (compile-gcc, sqlite3, regtest, 1)
   8m 1s        Run fuzz regression tests
   11m 46s      Run unit tests (compile-clang-sanitizers, 0)
   12m 59s      Compile CLN compile-gcc
   13m 42s      Compile CLN compile-clang
   14m 10s      Compile CLN compile-gcc-O3
   14m 15s      Compile CLN compile-clang-sanitizers
   15m 23s      Pre-build checks
   19m 37s      Test CLN dual-fund
   26m 49s      Run unit tests (compile-gcc, 1)
   43m 19s      Valgrind Test CLN Valgrind (06/10)
   43m 21s      Valgrind Test CLN Valgrind (08/10)
   43m 40s      Valgrind Test CLN Valgrind (05/10)
   43m 59s      Valgrind Test CLN Valgrind (03/10)
   44m 4s       Valgrind Test CLN Valgrind (07/10)
   47m 28s      Valgrind Test CLN Valgrind (09/10)
   47m 37s      Valgrind Test CLN Valgrind (02/10)
   47m 45s      Valgrind Test CLN Valgrind (01/10)
   52m 51s      Valgrind Test CLN Valgrind (04/10)
   54m 6s       Valgrind Test CLN Valgrind (10/10)
1h 14m 13s      Sanitizers Test CLN (ASan/UBSan (03/12), 3, --test-group=3 --test-group-count=12)
1h 14m 6s       Sanitizers Test CLN (ASan/UBSan (06/12), 6, --test-group=6 --test-group-count=12)
1h 15m 23s      Sanitizers Test CLN (ASan/UBSan (01/12), 1, --test-group=1 --test-group-count=12)
1h 20m 30s      Sanitizers Test CLN (ASan/UBSan (08/12), 8, --test-group=8 --test-group-count=12)
1h 22m 35s      Sanitizers Test CLN (ASan/UBSan (12/12), 12, --test-group=12 --test-group-count=12)
1h 23m 49s      Sanitizers Test CLN (ASan/UBSan (04/12), 4, --test-group=4 --test-group-count=12)
1h 26m 11s      Sanitizers Test CLN (ASan/UBSan (07/12), 7, --test-group=7 --test-group-count=12)
1h 28m 44s      Sanitizers Test CLN (ASan/UBSan (05/12), 5, --test-group=5 --test-group-count=12)
1h 29m 1s       Sanitizers Test CLN (ASan/UBSan (02/12), 2, --test-group=2 --test-group-count=12)
1h 29m 4s       Sanitizers Test CLN (ASan/UBSan (11/12), 11, --test-group=11 --test-group-count=12)
1h 31m 36s      Sanitizers Test CLN (ASan/UBSan (09/12), 9, --test-group=9 --test-group-count=12)
1h 38m 54s      Sanitizers Test CLN (ASan/UBSan (10/12), 10, --test-group=10 --test-group-count=12)
1h 39m 22s      Test CLN liquid
1h 52m 23s      Test minimum supported BTC v25.0 with clang
1h 52m 28s      Test CLN gcc
1h 53m 57s      Test CLN splicing
1h 57m 25s      Test CLN postgres
1h 59m 25s      Test CLN clang

2d 17h 56m 16s  TOTAL

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>