improve CI and lint

[ETeissonniere]

refactor our CI config to make better use of linters:

• run with latest releases of our testing dependencies
• update rustfmt config
• add support for clippy
• refactor CI action accordingly
• apply new listing recommendations (⚠️ lots of changes, mainly license header, clippy and fmt recommendations)
• update devcontainer to support clippy

likely to conflict with #603

[codecov]

Codecov Report

Merging #604 (eaf19ac) into master (1cb8bac) will increase coverage by 0.45%.
The diff coverage is 65.69%.

@@            Coverage Diff             @@
##           master     #604      +/-   ##
==========================================
+ Coverage   81.82%   82.28%   +0.45%     
==========================================
  Files          66       66              
  Lines        8508     7992     -516     
==========================================
- Hits         6962     6576     -386     
+ Misses       1546     1416     -130     

Impacted Files	Coverage Δ
nodes/main/src/command.rs	0.00% <0.00%> (ø)
nodes/main/src/executor.rs	0.00% <0.00%> (ø)
nodes/main/src/main.rs	0.00% <0.00%> (ø)
nodes/main/src/rpc.rs	0.00% <0.00%> (ø)
nodes/main/src/service.rs	0.00% <0.00%> (ø)
nodes/parachain/src/chain_spec.rs	0.00% <0.00%> (ø)
nodes/parachain/src/cli.rs	0.00% <0.00%> (ø)
nodes/parachain/src/rpc.rs	0.00% <0.00%> (ø)
nodes/parachain/src/service.rs	0.00% <0.00%> (ø)
nodes/staking/src/chain_spec.rs	0.00% <0.00%> (ø)
... and 78 more

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