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/0011-async-backing-6-seconds-rate.toml

@@ -8,13 +8,16 @@ chain = "rococo-local"
 [relaychain.genesis.runtimeGenesis.patch.configuration.config]
   needed_approvals = 4
   relay_vrf_modulo_samples = 6
-  scheduling_lookahead = 2
-  group_rotation_frequency = 4
 
 [relaychain.genesis.runtimeGenesis.patch.configuration.config.async_backing_params]
   max_candidate_depth = 3
   allowed_ancestry_len = 2
 
+[relaychain.genesis.runtimeGenesis.patch.configuration.config.scheduler_params]
+  lookahead = 2
+  group_rotation_frequency = 4
+
+
 [relaychain.default_resources]
 limits = { memory = "4G", cpu = "2" }
 requests = { memory = "2G", cpu = "1" }