Be more specific about NPM execution

[awharn]

Execute NPM directly in several Plugin interfaces.
Replace execSync with spawnSync.
Update tests to deal with this change.

[codecov]

Codecov Report

Base: 82.70% // Head: 82.70% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (68750f8) compared to base (5cf170b).
Patch coverage: 72.22% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##           zowe-v1-lts     #900   +/-   ##
============================================
  Coverage        82.70%   82.70%           
============================================
  Files              163      163           
  Lines             7948     7945    -3     
  Branches          1454     1454           
============================================
- Hits              6573     6571    -2     
+ Misses            1371     1370    -1     
  Partials             4        4           

Impacted Files	Coverage Δ
...s/imperative/src/plugins/utilities/NpmFunctions.ts	61.53% <37.50%> (-1.26%)	⬇️
...e/src/plugins/utilities/npm-interface/uninstall.ts	97.05% <100.00%> (ø)
...erative/src/plugins/utilities/runValidatePlugin.ts	100.00% <100.00%> (ø)

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[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

72.2% Coverage
0.0% Duplication

[github-actions]

Release succeeded for the zowe-v1-lts branch. 🎉

The following packages have been published:

• npm: @zowe/imperative@4.18.10

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