[anodized-core] refactor: clean up Pre/PostConditions #851

Job	Run time
Check formatting	18s
Lint and test anodized-fmt	31s
Lint and test anodized-core	23s
Lint and smoke-test fuzz targets	1m 52s
Lint and smoke-test the `bin-search` example	1m 15s
Lint and test anodized with cfg ``	35s
Lint test-util	18s
Lint and test anodized-logic	34s
Lint and test anodized with cfg `--config 'build.rustflags=["--cfg","anodized_panic"]'`	45s
Lint and test anodized with cfg `--config 'build.rustflags=["--cfg","anodized_print","--cfg","anodized_panic"]'`	32s
Lint and test anodized with cfg `--config 'build.rustflags=["--cfg","anodized_print","--cfg","anodized_panic","--cfg","anodized_try"]'`	56s
Lint and test anodized with cfg `--config 'build.rustflags=["--cfg","anodized_discard_specs"]'`	41s
Lint and test anodized with cfg `--config 'build.rustflags=["--cfg","anodized_print"]'`	36s
	9m 16s

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