Remove mock adapter from environment struct

[b-gopalswami]

Removing mock adapter from Environment struct as this is more of test stuffs. As this struct *test_env.CLClusterTestEnv is exposed now, can consume mock adapter from it directly instead of adding it to Environment struct.

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AER Report: CI Core ran successfully ✅

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[github-actions]

I see you updated files related to core. Please run pnpm changeset in the root directory to add a changeset as well as in the text include at least one of the following tags:

• #added For any new functionality added.
• #breaking_change For any functionality that requires manual action for the node to boot.
• #bugfix For bug fixes.
• #changed For any change to the existing functionality.
• #db_update For any feature that introduces updates to database schema.
• #deprecation_notice For any upcoming deprecation functionality.
• #internal For changesets that need to be excluded from the final changelog.
• #nops For any feature that is NOP facing and needs to be in the official Release Notes for the release.
• #removed For any functionality/config that is removed.
• #updated For any functionality that is updated.
• #wip For any change that is not ready yet and external communication about it should be held off till it is feature complete.

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