fix: getBlockWithTx* fetch block header and txns separately

[brbrr]

fixes #3261

[Copilot]

Pull request overview

This PR refactors block fetching to separate header and transaction retrieval as part of fixing issue #3261. The change aims to optimize performance by allowing header and transaction data to be fetched independently rather than always fetching the entire block.

Key changes:

• Added new blockTxnsByNumber helper method and TransactionsByBlockNumber blockchain reader method to fetch transactions separately
• Refactored BlockWithTxHashes and BlockWithTxs to call blockHeaderByID and blockTxnsByNumber separately instead of blockByID
• Updated blockStatus signature to accept block number directly instead of the full block

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
rpc/v9/helpers.go	Added new blockTxnsByNumber helper to fetch transactions by block number
rpc/v9/block.go	Refactored BlockWithTxHashes and BlockWithTxs to use separate header and transaction fetches; updated blockStatus to accept block number
blockchain/blockchain.go	Added new TransactionsByBlockNumber method to Reader interface and implementation
mocks/mock_blockchain.go	Added mock implementation for TransactionsByBlockNumber method

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[codecov]

Codecov Report

❌ Patch coverage is 72.60274% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.26%. Comparing base (d0c941b) to head (ef1acb0).

Files with missing lines	Patch %	Lines
rpc/v10/helpers.go	52.94%	6 Missing and 2 partials ⚠️
rpc/v8/helpers.go	52.94%	6 Missing and 2 partials ⚠️
rpc/v9/helpers.go	52.94%	6 Missing and 2 partials ⚠️
blockchain/blockchain.go	0.00%	4 Missing ⚠️
rpc/v10/block.go	87.87%	2 Missing and 2 partials ⚠️
rpc/v8/block.go	86.20%	2 Missing and 2 partials ⚠️
rpc/v9/block.go	86.20%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3322      +/-   ##
==========================================
+ Coverage   76.20%   76.26%   +0.05%     
==========================================
  Files         346      346              
  Lines       32713    32816     +103     
==========================================
+ Hits        24930    25027      +97     
+ Misses       5993     5987       -6     
- Partials     1790     1802      +12     

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