Rename DelMarkerExpiration to DeletedObjectExpiration

[krisis]

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Description

Rename the recently introduced ILM action DelMarkerExpiration to DeletedObjectExpiration. This action is not yet usable without the necessary client-side support like mc for e.g.

Motivation and Context

DeletedObjectExpiration captures two important consequences of this ILM action better.

1. It applies on a deleted object, i.e an object with DEL marker as its current (latest) version.
2. It removes the entire object, i.e all current and noncurrent versions of a qualifying deleted object.

How to test this PR?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[harshavardhana]

Is this ready? @krisis