Cleanup all unused files and update Readme

[1xstj]

Summary of changes Changes introduced in this pull request:

• Removes parachain directory
• Remove chainspec dir, this is not needed since we dont run a testnet from this repo
• Remove docker action, we publish docker images for tangle
• Remove unused config files and scripts
• Unify local testnet script
• Update readme on running local testnet

Reference issue to close (if applicable)

Closes

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (a1ac55a) 19.43% compared to head (86aba24) 19.43%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #661 +/- ## ======================================= Coverage 19.43% 19.43% ======================================= Files 77 77 Lines 5641 5641 ======================================= Hits 1096 1096 Misses 4545 4545 ```

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