Add api to get eth call executor state and error count

[maxkozlovsky]

Add monad_eth_call_executor_get_state() to get counts of currently executing/queued requests and error counts.

Add counter for currently executing requests.

Add counter for number of times the queue was full. Previously this was tracked in rpc code, but was not correctly accounting for the second pool and for possibility of request retried in high pool.

[Copilot]

Pull Request Overview

This PR adds an API to monitor the state and error counts of the eth call executor, enabling better observability of the request processing system.

• Adds new state structures to expose pool statistics including executing/queued request counts and queue full conditions
• Implements tracking of currently executing requests and queue full errors within the pool logic
• Provides a new public API monad_eth_call_executor_get_state() to retrieve these statistics

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
category/rpc/eth_call.h	Defines new state structures and declares the get_state API function
category/rpc/eth_call.cpp	Implements state tracking counters and the get_state functionality
category/core/fiber/priority_pool.hpp	Adds num_fibers() method to expose fiber count

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