test: add end-to-end testing framework (#5435)

Partial fix for #5291. For details, see [README.md](https://github.com/tendermint/tendermint/blob/erik/e2e-tests/test/e2e/README.md) and [RFC-001](https://github.com/tendermint/tendermint/blob/master/docs/rfc/rfc-001-end-to-end-testing.md).

This only includes a single test case under `test/e2e/tests/`, as a proof of concept - additional test cases will be submitted separately. A randomized testnet generator will also be submitted separately, there a currently just a handful of static testnets under `test/e2e/networks/`. This will eventually replace the current P2P tests and run in CI.

test/e2e/runner/wait.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	e2e "github.com/tendermint/tendermint/test/e2e/pkg"
+)
+
+// Wait waits for a number of blocks to be produced, and for all nodes to catch
+// up with it.
+func Wait(testnet *e2e.Testnet, blocks int64) error {
+	block, _, err := waitForHeight(testnet, 0)
+	if err != nil {
+		return err
+	}
+	waitFor := block.Height + blocks
+	logger.Info(fmt.Sprintf("Waiting for all nodes to reach height %v...", waitFor))
+	_, err = waitForAllNodes(testnet, waitFor, 20*time.Second)
+	if err != nil {
+		return err
+	}
+	return nil
+}