feat(nns): Move neuron validation to timer (#3181) #618

Job	Run time
Bazel System Test Nightly	22m 30s
Bazel System Test Staging	8m 43s
Bazel System Test Hotfix	10m 32s
Dependency Scan for Release	3m 28s
Setting up guest os qualification pipeline	9s
CI Main / Bazel Test All	18m 47s
CI Main / Bazel Test macOS Intel	1h 2m 21s
CI Main / Bazel Build All Config Check	0s
CI Main / Bazel Build Fuzzers	2m 50s
CI Main / Bazel Build Fuzzers AFL	10m 17s
CI Main / Build IC	16m 38s
CI Main / Cargo Clippy Linux	27s
CI Main / Python CI Tests	3m 51s
CI Main / Cargo Build Release Linux	23s
Qualifying d9fe2076f677a08734bed90c67b1c3f4056ed621 -> bdb7c71b590e33040fa721eac1936ab108a65a96	1h 17m 19s
CI Main / Build Determinism	0s
	3h 58m 15s

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