There's a bit of YAML configuration changes and plumbing work in order to support being able to specify the all_nodes_electable parameter from SERVER-30683 for the ReplicaSetFixture instances that the ShardedClusterFixture spawns.

• A config_options parameter should be added to the ShardedClusterFixture constructor. The parameter should default to an empty dictionary to avoid any impact on existing usages of the ShardedClusterFixture class by other test suites. The arguments to the ReplicaSetFixture constructed in ShardedClusterFixture#_new_configsvr() should be merged according to the following rules of precedence:
  1. The hardcoded values in ShardedClusterFixture#_new_configsvr().
  2. The contents of config_options.
  3. The contents of mongod_options.
  4. Any shared parameters specified to the ShardedClusterFixture constructor.
• A shard_options parameter should be added to the ShardedClusterFixture constructor. The parameter should default to an empty dictionary to avoid any impact on existing usages of the ShardedClusterFixture class by other test suites. The arguments to the ReplicaSetFixture constructed in ShardedClusterFixture#_new_rs_shard() should be merged according to the following rules of precedence:
  1. The hardcoded values in ShardedClusterFixture#_new_rs_shard().
  2. The contents of shard_options.
  3. The contents of mongod_options.
  4. Any shared parameters specified to the ShardedClusterFixture constructor.