Fix merged-mined parent template refresh when child template changes

[MoneroOcean]

Motivation

• An early-return in setNewBlockTemplate compared only idHash and could skip rebuilding a merged-mined parent template that had a newly-derived parent_blocktemplate_blob, leaving parent templates referencing stale child state.
• The change restores correctness for merged-mining refreshes while keeping the fast-path for truly unchanged templates.

Description

• Updated lib/pool/templates.js in setNewBlockTemplate to skip the early return when the incoming template is a merged-mined parent (has parent_blocktemplate_blob) and the parent_blocktemplate_blob differs from the active template, forcing reconstruction of the BlockTemplate in that case.
• Preserved the unchanged-template fast path for non-MM templates and for MM templates whose parent_blocktemplate_blob is unchanged.
• No other behavioral changes; the fix is a minimal guard around the existing idHash equality check.

Testing

• Loaded the modified module with node -e "require('./lib/pool/templates.js')" which completed successfully.
• No full test-suite run was performed in this environment due to external dependency constraints, so only the basic module load check was executed and passed.

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Codex Task