feat(erpc:PLA-696): add declarative policy mode and method workload profiles

[0x666c6f]

Summary

• add declarative selectionPolicy.rules mode with explicit precedence (evalFunction > rules > built-in default)
• add reusable method workload profiles (methods.profiles) with per-method binding (methods.definitions.<method>.profile)
• support profile components: cache, failsafe, routing, multiplex
• add method-level multiplex override (methods.definitions.<method>.multiplex)
• extend config analyzer report with explain lines for policy path and profile binding path/components

Validation

• go test ./common
• go test ./erpc -run 'TestPolicyEvaluator_DeclarativeRules|TestNetwork_Multiplexer_MethodLevelDisable|TestGenerateValidationReport_ExplainIncludesPolicyAndProfilePath|TestNetwork_Multiplexer_FollowersReceiveResponse'
• go test ./erpc -run '^$'

Linear: https://linear.app/morpho-labs/issue/PLA-696/erpc-versatility-declarative-policy-mode-method-workload-profiles

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