Move EVM's proxy API function pointers into BPL mpool

[keegan-moore]

Describe the contribution

This PR moves the EVM's proxy API function pointers into the existing mpool struct (in BPL).

The related PR for BPLib is here: keegan-moore/bplib#2

This work is based off of another feature, related to these two PRs:

1. Add initial prototype Event Management files bplib#1
2. Add prototype Event Management calls and Event Proxy impl files #1

Testing performed
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Expected behavior changes
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• API Change: xxx (if applicable)
• Behavior Change: xxx (if applicable)
• Or no impact to behavior

System(s) tested on

• Hardware: [e.g. PC, SP0, MCP750]
• OS: [e.g. Ubuntu 18.04, RTEMS 4.11, VxWorks 6.9]
• Versions: [e.g. cFE 6.6, OSAL 4.2, PSP 1.3 for mcp750, any related apps or tools]

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