Investigate RPC endpoints for completeness and correctness

[timwu20]

Issue summary

• Assess current state of implemented and unimplemented RPC calls
• Determine whether RPC calls are returning data as expected from latest version of Polkadot-js
• Create any issues required to address completeness or correctness
• Determine required core calls and tag issues with priority

Other information and links

• https://github.com/w3f/PSPs/blob/master/PSPs/drafts/psp-6.md
• https://polkadot.js.org/apps/#/explorer

• 1765

• 1761

• 1760

• 1759

• 1758

• 1757

• 1752

• 1721

• 1709

[EclesioMeloJunior]

Since we close the issue https://github.com/ChainSafe/gossamer/issues/1765 we can mark state_call as fixed

[P1sar]

Check this issues as part of this Epic https://github.com/ChainSafe/gossamer/issues/265 and https://github.com/ChainSafe/gossamer/issues/2531