feat(dot/parachain/backing): Implement Statement Table

[kishansagathiya]

Issue summary

• Table represents the table of candidates and statements under the relay-parent.

• as of now, we have a Table Interface instead of a Table struct
  https://github.com/ChainSafe/gossamer/pull/3532/files#diff-3ec19efc560ad085b750d7d615cb53487e7261181e390099fbb5b2e52b39102d

• We need to add the table structure and implement the interface.

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• The statement table stores messages other authorities(parachain validators) issue about candidates(parachain blocks).

• These messages create a proposal submitted to a BFT(Byzantine Fault Tolerance) consensus process.

• Proposals are formed of sets of candidates which have the requisite number of validity and availability votes.

• Each parachain is associated with a committee of authorities, who issue statements indicating whether the candidate is valid or invalid. Once a threshold of the committee has signed validity statements, the candidate may be marked includable.

Sub issues

• Implement a function to get committed candidate receipt for the given candidate hash
• Implement a function to import a signed statement.
• Implement a function to get attested candidate for the given candidate hash
• drain missbehaviours

Other information and links

• Reference code in polkadot-sdk:
  https://github.com/paritytech/polkadot-sdk/blob/7ca0d65f19497ac1c3c7ad6315f1a0acb2ca32f8/polkadot/node/core/backing/src/lib.rs#L214-L215