Remove pending _type usages from the codebase

[dreamer-89]

Creating this issue to list down pending _type usages from code bsae. Quick search on _type reveals below pending issues. More discussion here #2979 (comment)

• Run bulk index benchmark takes user input for typeName. Code usage, defined here. type is taken as input from CLI. Is this benchmark still used today ? [Type removal] Remove _type support in NOOP bulk indexing from client benchmark #3076
• BulkRequestParser.java has elseif check on _type field. This check should be removed as _type should be addressed as any other random word in request body; which is already handled here. See this added previously and referred in BulkRequestParserTests inside testTypesStillParsedForBulkMonitoring. [Type removal] Remove type from BulkRequestParser #3423
• Can we remove type validation from MapperService & clean up tests. In 2.0 no type field is accepted and older indices would have already been validated.

Identified other references which can be removed without any issue.

• ScriptProcessor, ConditionalProcessor. Is it possible to provide _type from curl request and get these deprecations ? [Type removal] Remove _type deprecation from script and conditional processor #3239
• Multiple references of _type in _ingest/pipeline/_simulate API across multiple places. Verified that _type is ignored by engine. Reference in a. IngestRequestConverterTests.java b. IngestClientIT.java in testSimulatePipeline c. grok_120.yml yaml tests [Type removal] Remove redundant _type in pipeline simulate action #3371
• ForEachProcessorTests.java need to remove fieldValue in TestProcessor constructor. [Type removal] Remove _type from _bulk yaml test, scripts, unused constants #3372
• 60_deprecated.yml verifying deprecated type in bulk action. [Type removal] Remove _type from _bulk yaml test, scripts, unused constants #3372
• CustomScriptPlugin adds _type field. Probably ignored on engine side and thus can be removed [Type removal] Remove _type from _bulk yaml test, scripts, unused constants #3372
• MultiTermVectorsResponse.java has _type defined in Fields class. It is not referenced and can be removed. [Type removal] Remove _type from _bulk yaml test, scripts, unused constants #3372
• UpdateHelper.java defines _type in ContextFields but not referenced anywhere. [Type removal] Remove _type from _bulk yaml test, scripts, unused constants #3372
• Bunch of _type references in mocked API responses of reindex module modules/reindex/src/test/resources/responses/*.json [Type removal] _type removal from mocked responses of scroll hit tests #3377
• Tests for tests ClientYamlTestSuitesTests, DoSectionTests, OpenSearchClientYamlSuiteTestCaseTests have hard-coded request body. [Type removal] _type removal from tests of yaml tests #3406
• HLRC TermsVectorRequest, CountRequest and tests still uses _type in toXContent.

[dreamer-89]

Closing this issue and target remaining type removal in #2979 post 2.0 release.