DRILL-6492: Ensure schema / workspace case insensitivity in Drill 1. StoragePluginsRegistryImpl was updated: a. for backward compatibility at init to convert all existing storage plugins names to lower case, in case of duplicates, to log warning and skip the duplicate. b. to wrap persistent plugins registry into case insensitive store wrapper (CaseInsensitivePersistentStore) to ensure all given keys are converted into lower case when performing insert, update, delete, search operations. c. to load system storage plugins dynamically by @SystemStorage annotation. 2. StoragePlugins class was updated to stored storage plugins configs by name in case insensitive map. 3. SchemaUtilities.searchSchemaTree method was updated to convert all schema names into lower case to ensure that are they are matched case insensitively (all schemas are stored in Drill in lower case). 4. FileSystemConfig was updated to store workspaces by name in case insensitive hash map. 5. All plugins schema factories are now extend AbstractSchemaFactory to ensure that given schema name is converted to lower case. 6. New method areTableNamesAreCaseInsensitive was added to AbstractSchema to indicate if schema tables names are case insensitive. By default, false. Schema implementation is responsible for table names case insensitive search in case it supports one. Currently, information_schema, sys and hive do so. 7. System storage plugins (information_schema, sys) were refactored to ensure their schema, table names are case insensitive, also the annotation @SystemPlugin and additional constructor were added to allow dynamically load system plugins at storage plugin registry during init phase. 8. MetadataProvider was updated to concert all schema filter conditions into lower case to ensure schema would be matched case insensitively. 9. ShowSchemasHandler, ShowTablesHandler, DescribeTableHandler were updated to ensure schema / tables names (this depends if schema supports case insensitive table names) would be found case insensitively.