Add memory cache for EntityFieldManager

Problem/Motivation

#3538006-8: Optimize EntityFieldManager::buildBundleFieldDefinitions() points out that it should use a memory cache, but it's kind of out of scope to add it in that issue.

Steps to reproduce

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Proposed resolution

Add a memory cache

Remaining tasks

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User interface changes

N/A

Introduced terminology

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API changes

Data model changes

N/A

Release notes snippet

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