docs(validators): onboarding guides for testnets+mainnet

[JafarAz]

Required for merge:

• pr-workflow-check / draft-release-check is ✅ success
• Other rules GitHub shows you, or can be read in configuration

Makes review faster:

• PR title is my best effort to provide summary of changes and has clear text to be part of release notes
• I marked PR by misc label if it should not be in release notes
• Linked Zenhub/Github/Slack/etc reference if one exists
• I was clear on what type of deployment required to release my changes (node, runtime, contract, indexer, on chain operation, frontend, infrastructure) if any in PR title or description
• Added reviewer into Reviewers
• I tagged(@) or used other form of notification of one person who I think can handle best review of this PR
• I have proved that PR has no general regressions of relevant features and processes required to release into production
• Any dependency updates made, was done according guides from relevant dependency
• Clicking all checkboxes
• Adding detailed description of changes when it feels appropriate (for example when PR is big)

[github-actions]

Pull reviewers stats

Stats of the last 30 days for composable:

	User	Total reviews	Time to review	Total comments
	dzmitry-lahoda	10	43m	2
	blasrodri	8	18h 47m	6
	RustNinja	8	16h 17m	0
	kkast	7	7h 25m	14
	JafarAz	7	1h 53m	3
	mina86	3	8h 14m	1
	fl-y	2	1d 19h 50m	0
	vmarkushin	1	16h 47m	4
	0xBrainjar2	1	4h 22m	0

[github-actions]

# run Composable node
nix run "github:ComposableFi/composable/refs/pull/4177/merge" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed

# run local Picasso DevNet (for CosmWasm development)
nix run "github:ComposableFi/composable/refs/pull/4177/merge#devnet-picasso" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed 

# CosmWasm on Substrate CLI tool
nix run "github:ComposableFi/composable/refs/pull/4177/merge#ccw" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed 

# run cross chain devnet with Dotsama and Cosmos nodes 
nix run "github:ComposableFi/composable/refs/pull/4177/merge#devnet-xc-fresh" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed 
# or same with docker
nix build "github:ComposableFi/composable/refs/pull/4177/merge#devnet-xc-image" --allow-import-from-derivation --extra-experimental-features "flakes nix-command" --no-sandbox --accept-flake-config --option sandbox relaxed \
&& docker load --input result && docker run -it --entrypoint bash devnet-xc:latest -c /bin/devnet-xc-fresh 

About nix