3D pricing metrics

[cloudspores]

This PR exposes the following metrics

1 Node's perception on the latest extraData contents (variable cost, fixed cost, eth gas price) as gauges under the PRICING_CONF category
1 Node's perception on Profitability levels of TxPool's contents (lo, hi, avg of transaction.priorityFeePerGas / TransactionProfitabilityCalculator.profitablePriorityFeePerGas(transaction)) as histogram under the TX_POOL_PROFITABILITY categoty
1 Same metrics as above, but in context of last sealed block (this is relevant only for Sequencer) as histogram under the SEQUENCER_PROFITABILITY category

Each metric category can be enabled indipendently, using the standard metrics-category option.

For histograms, it is possible to configure the buckets using the new conf option plugin-linea-profitability-metrics-buckets, that by default is set to 0.1, 0.3, 0.5, 0.7, 0.9, 1.0, 1.1, 1.2, 1.5, 2.0, 5.0, 10.0

names of the new exported metrics

# HELP linea_tx_pool_profitability_ratio_min Lowest transaction pool profitability ratio
# TYPE linea_tx_pool_profitability_ratio_min gauge
linea_tx_pool_profitability_ratio_min +Inf
# HELP linea_pricing_conf_values Profitability configuration values at runtime
# TYPE linea_pricing_conf_values gauge
linea_pricing_conf_values{field="fixed_cost_wei",} 3.0E7
linea_pricing_conf_values{field="eth_gas_price_wei",} 1.53525E8
linea_pricing_conf_values{field="variable_cost_wei",} 8.226788E9
# HELP linea_sequencer_profitability_ratio_max Highest sequencer profitability ratio
# TYPE linea_sequencer_profitability_ratio_max gauge
linea_sequencer_profitability_ratio_max{phase="pre_processing",} 16572.31055926643
linea_sequencer_profitability_ratio_max{phase="post_processing",} 0.0
# HELP linea_sequencer_profitability_ratio Sequencer profitability ratio buckets
# TYPE linea_sequencer_profitability_ratio histogram
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="0.9",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="1.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="1.2",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="2.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="5.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="10.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="100.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="1000.0",} 0.0
linea_sequencer_profitability_ratio_bucket{phase="pre_processing",le="+Inf",} 1.0
linea_sequencer_profitability_ratio_count{phase="pre_processing",} 1.0
linea_sequencer_profitability_ratio_sum{phase="pre_processing",} 16572.31055926643
# HELP linea_sequencer_profitability_ratio_min Lowest sequencer profitability ratio
# TYPE linea_sequencer_profitability_ratio_min gauge
linea_sequencer_profitability_ratio_min{phase="pre_processing",} 16572.31055926643
linea_sequencer_profitability_ratio_min{phase="post_processing",} +Inf
# HELP linea_tx_pool_profitability_ratio Transaction pool profitability ratio buckets
# TYPE linea_tx_pool_profitability_ratio histogram
linea_tx_pool_profitability_ratio_bucket{le="0.9",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="1.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="1.2",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="2.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="5.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="10.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="100.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="1000.0",} 0.0
linea_tx_pool_profitability_ratio_bucket{le="+Inf",} 0.0
linea_tx_pool_profitability_ratio_count 0.0
linea_tx_pool_profitability_ratio_sum 0.0
# HELP linea_tx_pool_profitability_ratio_max Highest transaction pool profitability ratio
# TYPE linea_tx_pool_profitability_ratio_max gauge
linea_tx_pool_profitability_ratio_max 0.0
# HELP linea_sequencer_profitability_ratio_created Sequencer profitability ratio buckets
# TYPE linea_sequencer_profitability_ratio_created gauge
linea_sequencer_profitability_ratio_created{phase="pre_processing",} 1.730398405758E9
# HELP linea_tx_pool_profitability_ratio_created Transaction pool profitability ratio buckets
# TYPE linea_tx_pool_profitability_ratio_created gauge
linea_tx_pool_profitability_ratio_created 1.730398404348E9

fixes https://github.com/Consensys/protocol-misc/issues/953

[garyschulte]

Non-blockion suggestions. LGTM