Remove direct Translog interaction from Engine

[Bukhtawar]

[Is your feature request related to a problem? Please describe.
As a part of #3241
We are exposing Translog directly from the TranslogManager, Ideally all operations to Translog should go via the manager itself

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OpenSearch/server/src/main/java/org/opensearch/index/translog/TranslogManager.java

Lines 100 to 103 in 22b42e4

	* @return the translog instance
	*/
	Translog getTranslog(boolean ensureOpen);

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