Remove AssignmentProviderConfig and use parameters from HostConfiguration instead (#3181)

This PR removes `AssignmentProviderConfig` and uses the corresponding
ondemand parameters from `HostConfiguration` instead. Additionally
`scheduling_lookahead` and all coretime/ondemand related parameters are
extracted in a separate struct - `SchedulerParams`.

The most relevant commit from the PR is [this
one](https://github.com/paritytech/polkadot-sdk/pull/3181/commits/830bc0f5e858944474171bbe33382ad96040b535).

Fixes https://github.com/paritytech/polkadot-sdk/issues/2268

---------

Co-authored-by: command-bot <>

polkadot/zombienet_tests/functional/0012-elastic-scaling-mvp.toml

@@ -3,9 +3,11 @@ timeout = 1000
 bootnode = true
 
 [relaychain.genesis.runtimeGenesis.patch.configuration.config]
-  max_validators_per_core = 2
   needed_approvals = 4
-  coretime_cores = 2
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config.scheduler_params]
+  max_validators_per_core = 2
+  num_cores = 2
 
 [relaychain]
 default_image = "{{ZOMBIENET_INTEGRATION_TEST_IMAGE}}"