Update network resolution by reusing resolve_network from helpers

[statxc]

Description

• Remove the duplicated NETWORK_MAP dict and _resolve_endpoint() function from cli/miner_commands/post.py
• Delegate to the existing resolve_network() in cli/issue_commands/helpers.py which handles the same priority chain (rpc-url > network flag > config > default)

No behavior change.

[anderdc]

Review of refactor/reuse-resolve-network

• Bug -- config network fallback dropped: The old _resolve_endpoint fell back to _load_config_value('network') when ws_endpoint was absent in config. resolve_network in helpers.py skips that -- if config['ws_endpoint'] is unset it jumps straight to the finney default (line 591). Users with only "network": "test" in ~/.gittensor/config.json will silently hit mainnet after this change. Fix: add a config.get('network') fallback branch in resolve_network between the ws_endpoint check and the finney default.

• Trailing-slash diff in NETWORK_MAP: The old post.py map had trailing / on test and finney URLs (wss://test.finney.opentensor.ai:443/). helpers.py omits the slash. Likely harmless for WS but worth confirming nothing downstream does exact-string comparison on endpoints.

• Wrapper can be inlined: _resolve_endpoint is called exactly once (ws_endpoint = _resolve_endpoint(network, rpc_url)). Replace with ws_endpoint, _ = resolve_network(network=network, rpc_url=rpc_url) and delete the wrapper.

• _load_config_value is NOT dead code: Still used for wallet and hotkey config lookups in miner_post. Do not remove.

[anderdc]

• Bug — config network fallback dropped: old _resolve_endpoint checked _load_config_value('network') when ws_endpoint was absent in config. resolve_network in helpers.py skips that — jumps straight to finney default (line 590). Users with only "network": "test" in ~/.gittensor/config.json will silently hit mainnet. Fix: add a config.get('network') fallback branch in resolve_network between the ws_endpoint check and the finney default.
• Wrapper can be inlined: _resolve_endpoint is called once — replace with ws_endpoint, _ = resolve_network(network=network, rpc_url=rpc_url) and delete the wrapper.

[statxc]

@anderdc I have updated. Thanks for your feedback.