R4R: LCD proof verification

[cwgoes]

Replaces #3191

Closes: #2432

Recreate the singleton verifier if the home directory has changed.

This means that LCD proofs now test lite client verification.

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added entries in PENDING.md with issue #
• rereviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[cwgoes]

Turns out LCD tests were not in fact using isolated directories, as they pass individually.

[cwgoes]

The problem is the singleton verifier, I think.

[codecov]

Codecov Report

Merging #3449 into develop will decrease coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #3449      +/-   ##
===========================================
- Coverage    59.49%   59.45%   -0.05%     
===========================================
  Files          135      135              
  Lines         9981     9981              
===========================================
- Hits          5938     5934       -4     
- Misses        3671     3675       +4     
  Partials       372      372