backup and restore staticVariableClassMap when processing heap dumps

[JimSuplizio]

What does this PR do?

When modifying the static variables for heap dump processing it turns out that the staticVariablesClassMap holds shallow copies of the ApexVariableContainers. What was happening is that these were getting modified as part of heap dump processing and not getting restored. The way this manifested itself was after stepping off checkpoint line one of static variable collections was showing all of the fields under "this". This was because of the variablesRef created when displaying the heap dump augmented variables had the same variablesRef value as "this" after things were restored and because the staticVariablesClassMap wasn't backed up with the rest of the stuff.

What issues does this PR fix or reference?

@W-5490706@

[lcampos]

I've confirmed this fixes the issue mentioned on the description and the issue with values not being fetch from debug log after using values from a heapdump.

[codecov]

Codecov Report

Merging #657 into develop will decrease coverage by 0.1%.
The diff coverage is 18.18%.

@@             Coverage Diff             @@
##           develop     #657      +/-   ##
===========================================
- Coverage    74.92%   74.82%   -0.11%     
===========================================
  Files          158      158              
  Lines         6394     6396       +2     
  Branches      1001     1001              
===========================================
- Hits          4791     4786       -5     
- Misses        1348     1355       +7     
  Partials       255      255

Impacted Files	Coverage Δ
...orcedx-apex-replay-debugger/src/core/logContext.ts	63.72% <18.18%> (-2.6%)	⬇️
...de-core/src/commands/forceStartApexDebugLogging.ts	43.66% <0%> (-2.5%)	⬇️
...ages/salesforcedx-vscode-core/src/context/index.ts	100% <0%> (ø)	⬆️

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[salesforce-cla]

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