Fix metrics breakages

[shemnon]

PR description

• Number of metrics labels need to match up with constructor
• Number of labels must be consistant, so I split it into two metrics
• Also, naming best practices say that sum() and avg() of a metric
  should be meaningful, separating into two metrics fixes that.
• fix style issues (finals, intellij warnings)

[shemnon]

This fixes a break at runtime - https://jenkins.pegasys.tech/job/Pantheon%20Benchmarks/job/Pantheon%20Master%20Automatic%20Benchmarks/job/master/583/console
with this stack:

picocli.CommandLine$ExecutionException: Error while running command (tech.pegasys.pantheon.cli.BlocksSubCommand$ImportSubCommand@6034e75d): java.lang.IllegalArgumentException: Incorrect number of labels.
	at picocli.CommandLine.execute(CommandLine.java:1168)
	at picocli.CommandLine.access$800(CommandLine.java:141)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:1367)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:1335)
	at picocli.CommandLine$AbstractParseResultHandler.handleParseResult(CommandLine.java:1243)
	at picocli.CommandLine.parseWithHandlers(CommandLine.java:1526)
	at tech.pegasys.pantheon.cli.ConfigOptionSearchAndRunHandler.handle(ConfigOptionSearchAndRunHandler.java:69)
	at tech.pegasys.pantheon.cli.ConfigOptionSearchAndRunHandler.handle(ConfigOptionSearchAndRunHandler.java:25)
	at picocli.CommandLine$AbstractParseResultHandler.handleParseResult(CommandLine.java:1243)
	at picocli.CommandLine.parseWithHandlers(CommandLine.java:1526)
	at tech.pegasys.pantheon.cli.PantheonCommand.parse(PantheonCommand.java:581)
	at tech.pegasys.pantheon.Pantheon.main(Pantheon.java:38)
Caused by: java.lang.IllegalArgumentException: Incorrect number of labels.
	at io.prometheus.client.SimpleCollector.labels(SimpleCollector.java:64)
	at tech.pegasys.pantheon.metrics.prometheus.PrometheusCounter.labels(PrometheusCounter.java:28)
	at tech.pegasys.pantheon.metrics.prometheus.PrometheusCounter.labels(PrometheusCounter.java:18)
	at tech.pegasys.pantheon.ethereum.core.PendingTransactions.<init>(PendingTransactions.java:79)
	at tech.pegasys.pantheon.ethereum.eth.transactions.TransactionPoolFactory.createTransactionPool(TransactionPoolFactory.java:34)
	at tech.pegasys.pantheon.controller.MainnetPantheonController.init(MainnetPantheonController.java:151)
	at tech.pegasys.pantheon.controller.PantheonController.fromConfig(PantheonController.java:61)
	at tech.pegasys.pantheon.cli.PantheonControllerBuilder.build(PantheonControllerBuilder.java:109)
	at tech.pegasys.pantheon.cli.PantheonCommand.buildController(PantheonCommand.java:690)
	at tech.pegasys.pantheon.cli.BlocksSubCommand$ImportSubCommand.run(BlocksSubCommand.java:125)
	at picocli.CommandLine.execute(CommandLine.java:1160)
	... 11 more

In a follow-on CL I will investigate not using no-op metrics in test, or making no-op metrics require label counts to match.

[ajsutton]

LGTM. Only thing I wonder is if we should leave NoOpMetrics as really doing nothing and have a TestMetrics that performs the number-of-labels check.

I guess the other possibility (in a future PR) would be to have variants of LabelledMetric for the number of labels so we get compile time checking. I suspect any metric with more than 3 labels is probably very suspect.

[rojotek]

LGTM