[SPARK-14636] Add minimum memory checks for drivers and executors

## What changes were proposed in this pull request?

Implement the same memory size validations for the StaticMemoryManager (Legacy) as the UnifiedMemoryManager has.

## How was this patch tested?

Manual tests were done in CDH cluster.

Test with small executor memory:
`
spark-submit --class org.apache.spark.examples.SparkPi --deploy-mode client --master yarn --executor-memory 15m --conf spark.memory.useLegacyMode=true /opt/cloudera/parcels/CDH/lib/spark/examples/lib/spark-examples*.jar 10
`

Exception thrown:
```
ERROR spark.SparkContext: Error initializing SparkContext.
java.lang.IllegalArgumentException: Executor memory 15728640 must be at least 471859200. Please increase executor memory using the --executor-memory option or spark.executor.memory in Spark configuration.
	at org.apache.spark.memory.StaticMemoryManager$.org$apache$spark$memory$StaticMemoryManager$$getMaxExecutionMemory(StaticMemoryManager.scala:127)
	at org.apache.spark.memory.StaticMemoryManager.<init>(StaticMemoryManager.scala:46)
	at org.apache.spark.SparkEnv$.create(SparkEnv.scala:352)
	at org.apache.spark.SparkEnv$.createDriverEnv(SparkEnv.scala:193)
	at org.apache.spark.SparkContext.createSparkEnv(SparkContext.scala:289)
	at org.apache.spark.SparkContext.<init>(SparkContext.scala:462)
	at org.apache.spark.examples.SparkPi$.main(SparkPi.scala:29)
	at org.apache.spark.examples.SparkPi.main(SparkPi.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:731)
	at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:181)
	at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:206)
	at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:121)
	at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
```

Author: Peter Ableda <peter.ableda@cloudera.com>

Closes #12395 from peterableda/SPARK-14636.