FmpDevicePkg: Improve library documentation [Rebase & FF]

[os-d]

Description

Adds a ReadMe.md to each library instance and updates FmpDevicePkg_ReadMe.md to reference available library documentation.

Cherry-picked from: 61d7c67.

• Impacts functionality?
  • Functionality - Does the change ultimately impact how firmware functions?
  • Examples: Add a new library, publish a new PPI, update an algorithm, ...
• Impacts security?
  • Security - Does the change have a direct security impact on an application,
    flow, or firmware?
  • Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
• Breaking change?
  • Breaking change - Will anyone consuming this change experience a break
    in build or boot behavior?
  • Examples: Add a new library class, move a module to a different repo, call
    a function in a new library class in a pre-existing module, ...
• Includes tests?
  • Tests - Does the change include any explicit test code?
  • Examples: Unit tests, integration tests, robot tests, ...
• Includes documentation?
  • Documentation - Does the change contain explicit documentation additions
    outside direct code modifications (and comments)?
  • Examples: Update readme file, add feature readme file, link to documentation
    on an a separate Web page, ...

How This Was Tested

From 2311.

Integration Instructions

N/A.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release/202405@14a359e). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/202405     #300   +/-   ##
=================================================
  Coverage                  ?   86.59%           
=================================================
  Files                     ?       13           
  Lines                     ?     2126           
  Branches                  ?      306           
=================================================
  Hits                      ?     1841           
  Misses                    ?      269           
  Partials                  ?       16           

Flag	Coverage Δ
FmpDevicePkg	63.79% <ø> (?)
SecurityPkg	91.05% <ø> (?)

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