Convert ENCRYPTION_STRICT_MODE (`option.Config.EnableEncryptionStrictMode`) to load-time config

Convert this macro to use DECLARE_CONFIG or NODE_CONFIG for runtime configuration.

Current definition location: pkg/datapath/linux/config/config.go:240-262

if option.Config.EnableEncryptionStrictMode {
    cDefinesMap["ENCRYPTION_STRICT_MODE"] = "1"
}

BPF usage: Used to enforce strict encryption mode where all traffic must be encrypted

Configuration source: option.Config.EnableEncryptionStrictMode