Elastic scaling: add e2e test (#3929)

On top of https://github.com/paritytech/polkadot-sdk/pull/3879

I've also moved the previous test where we ensure multiple cores per
para doesn't break non elastic parachains.

---------

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
Co-authored-by: Javier Viola <363911+pepoviola@users.noreply.github.com>

polkadot/zombienet_tests/elastic_scaling/0002-elastic-scaling-doesnt-break-parachains.toml

@@ -0,0 +1,40 @@
+[settings]
+timeout = 1000
+bootnode = true
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config]
+  needed_approvals = 4
+
+[relaychain.genesis.runtimeGenesis.patch.configuration.config.scheduler_params]
+  max_validators_per_core = 2
+  num_cores = 2
+
+[relaychain]
+default_image = "{{ZOMBIENET_INTEGRATION_TEST_IMAGE}}"
+chain = "rococo-local"
+default_command = "polkadot"
+
+[relaychain.default_resources]
+limits = { memory = "4G", cpu = "2" }
+requests = { memory = "2G", cpu = "1" }
+
+  [[relaychain.nodes]]
+  name = "alice"
+  validator = "true"
+
+  [[relaychain.node_groups]]
+  name = "validator"
+  count = 3
+  args = [ "-lparachain=debug,runtime=debug"]
+
+[[parachains]]
+id = 2000
+default_command = "polkadot-parachain"
+add_to_genesis = false
+register_para = true
+onboard_as_parachain = false
+
+  [parachains.collator]
+  name = "collator2000"
+  command = "polkadot-parachain"
+  args = [ "-lparachain=debug" ]