Examples: switch to use rococo node

[haerdib]

This PR updates the following:

• Switches CI testing node to polkadot docker image, which is regularly updated and uses ../latest. The dev runtime is rococo.
• Added a new Runtime Config, which matches the rococo polkadot runtime:

pub type RococoRuntimeConfig = WithAddress<DefaultRuntimeConfig, MultiAddress<AccountId32, ()>>;

• Default Runtime was switched to be the "original" defined one. This makes the generation of the rococo_runtime_config a little bit more comprehensible / traceable.
• The following tests were removed:
  • staking
  • contracts
  • identity
    Reasoning: Staking and contracts pallet are not available on the Rococo runtime. The Identity pallet is available, but the calls are filtered: https://github.com/paritytech/polkadot-sdk/blob/cc7ebe054038186c8a7409f54c4008ddc82a5ad0/polkadot/runtime/rococo/src/lib.rs#L189-L198
• Created a new wasm binary for the runtime upgrade: needed a higher spec version (must be higher than the original one) and a renaming of the runtime (needs to have the same name as the old one)

closes #778

[Niederb]

I like the changes. I think it makes sense to use the rococo runtime as this one should be better maintained.

[Niederb]

Do we have documentation on how to get this file and what version this currently is?

[haerdib]

I built it myself. But effectively it can be any runtime, as long as the spec_version is higher than the original one and the runtime name matches the old one. I only took the minimal one to make sure it builds faster.

Should I add a documentation for this?

[Niederb]

Would be great to have some documentation 👍

[Niederb]

I think flipper.wasm is not used anymore

[haerdib]

Good catch, thanks!

[Niederb]

Nice. Thanks for the updated documentation 👍