build largest two RAM consumers, nimbus_beacon_node and all_tests, by default separately

[tersec]

Hopefully mitigate the Windows OOMs; followup to #4495 #4502 #4504

$ make test
Building: install/usr/lib/libbacktracenim.a
Building: build/generate_makefile
Build completed successfully: build/generate_makefile
Building: build/consensus_spec_tests_mainnet
Building: build/consensus_spec_tests_minimal
Building: build/state_sim
Building: build/block_sim
... only later ...
Build completed successfully: build/state_sim
Build completed successfully: build/block_sim
Build completed successfully: build/consensus_spec_tests_minimal
Build completed successfully: build/consensus_spec_tests_mainnet
Building: build/all_tests

and similar for nbc

[etan-status]

Oh, cool. Hope that finally makes Windows stable again. Appreciate all the effort, especially given the day/time

[github-actions]

Unit Test Results

         9 files  ±0    1 050 suites  ±0   33m 54s ⏱️ +20s
  3 512 tests ±0    3 275 ✔️ ±0  237 💤 ±0  0 ❌ ±0 
15 269 runs  ±0  15 004 ✔️ ±0  265 💤 ±0  0 ❌ ±0 

Results for commit f74b825. ± Comparison against base commit 7ad0d3e.