Draft: [SDAO-297] morley-client: Extend NodeMethods so specific blocks can be queried

Description

Problem: For SDAO-297, we need to query big maps and contract storage at specific blocks.

Solution:

• NodeMethods is extended with new methods getStorageAtBlock and getBigMapValueAtBlock
• A BlockId type is added that represents different types of block IDs.

Related issue(s)

https://issues.serokell.io/issue/SDAO-297

TODOs (please discuss)

• For consistency, the Text arguments in getBlockConstants and getHeadBlockOperations are changed to BlockIds
• To avoid confusion, getHeadBlockOperations is renamed to getBlockOperations
• For consistency, the remaining methods that are currently specialized to query the head block are generalized to take a BlockId argument
• To avoid unnecessary growth in NodeMethods, turn "non-primitive" methods like getStorage and getBigMapValue into top-level definitions

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