Implement `chainsync` `ChainReader` with `pallas`

[jpraynaud]

Content

This PR includes an implementation of

• ChainReader trait
• PallasChainReader implementation of the chainsync mini protocol with pallas
• FakeChainReader fake implementation

Pre-submit checklist

• Branch
  • [x] Tests are provided (if possible)
  • [x] Crates versions are updated (if relevant)
  • [x] CHANGELOG file is updated (if relevant)
  • [x] Commit sequence broadly makes sense
  • [x] Key commits have useful messages
• PR
  • [x] No clippy warnings in the CI
  • [x] Self-reviewed the diff
  • [x] Useful pull request description
  • [x] Reviewer requested

Issue(s)

Closes #1590

[github-actions[bot]]

Test Results

    3 files  ±0     43 suites  ±0   8m 32s :stopwatch: -2s   991 tests +4    991 :white_check_mark: +4  0 :zzz: ±0  0 :x: ±0  1 089 runs  +4  1 089 :white_check_mark: +4  0 :zzz: ±0  0 :x: ±0 

Results for commit 968f0b98. ± Comparison against base commit 7b089742.

:recycle: This comment has been updated with latest results.