refactor: generic extension crate to de-duplicate code between runtimes

[chungquantin]

Description

Removing the extension from the devnet and testnet runtimes. Make sure that adding features in the future for one runtime does not impact the other runtimes.

CHANGELOG

• Separate the extension from runtimes to standalone crate pop-runtime-extension in runtime/extension
• Preview the integration of pop-runtime-extension crate to pop-runtime-testnet: (no merge) refactor: migrate testnet chain extension #167
• Encoding / decoding dispatch error test module is currently defined inside pop-runtime-devnet. This can be improved in the another PR to make something like TestSuiteBuilder that can be reused in multiple runtimes.

How feature can be added in the future?

Create a struct Extension and implement the ReadState trait and CallFilter trait for the Extension to handle the queries from the contract environment.

[evilrobot-01]

Looks good, just missing doc comments as a finishing touch.

Strange that there is no code coverage report added to this PR, nor the base branch. I'll see if I can get that resolved.

[evilrobot-01]

Two last suggestions to simplify the language on the comments and then good to go!

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 41.72662% with 162 lines in your changes missing coverage. Please review.

Please upload report for BASE (daan/api@1acbd21). Learn more about missing BASE report.

Files	Patch %	Lines
extension/src/lib.rs	8.00%	138 Missing ⚠️
extension/src/tests.rs	88.03%	0 Missing and 14 partials ⚠️
runtime/devnet/src/config/api.rs	0.00%	10 Missing ⚠️

@@             Coverage Diff             @@
##             daan/api     #163   +/-   ##
===========================================
  Coverage            ?   31.43%           
===========================================
  Files               ?       34           
  Lines               ?     2885           
  Branches            ?     2885           
===========================================
  Hits                ?      907           
  Misses              ?     1955           
  Partials            ?       23           

Files	Coverage Δ
extension/src/v0.rs	100.00% <100.00%> (ø)
runtime/devnet/src/config/contracts.rs	60.00% <ø> (ø)
runtime/devnet/src/lib.rs	17.31% <ø> (ø)
runtime/devnet/src/config/api.rs	0.00% <0.00%> (ø)
extension/src/tests.rs	88.03% <88.03%> (ø)
extension/src/lib.rs	8.00% <8.00%> (ø)

[evilrobot-01]

LGTM, thanks for your patience!