Updating SystTool module for Dependent dials

[jedori0228]

This PR will handle "dependent" dials properly.
For instance, now we can group dependent dials (e.g., FSI knobs) and throw multisim universes. An example output from UniverseOracle looks like below:

 72: GENIEReWeight_ICARUS_v1_multisim_FSI_pi_VariationResponse, type 0, 100 universes, adjusted parameters:
    FrAbs_pi
    FrCEx_pi
    FrInel_pi
    MFP_pi

[jedori0228]

To handle "single universe" parameters introduced in SBNSoftware/icaruscode#612, additional updates are made.
When we write single element in <param_name>_variation_descriptor in the nusyst configuration file

    VecFFCCQEshape_central_value: 0
    VecFFCCQEshape_variation_descriptor: "[1.0]"

GenerateSystProviderConfig will make SystParamHeader::paramVariations empty, but SystParamHeader::centralParamValue is updated to 1.0 and SystParamHeader::isCorrection is set to true.
In 58c6946, now we treat isCorrection==true cases properly.

[miquelnebot]

trigger build SBNSoftware/icaruscode#612

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✔️ CI build for LArSoft Succeeded on slf7 for e20:prof -- details available through the CI dashboard

[FNALbuild]

⚠️ CI build for ICARUS Warning at phase ci_tests ICARUS on slf7 for c7:prof -- details available through the CI dashboard

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[FNALbuild]

⚠️ CI build for ICARUS Warning at phase ci_tests ICARUS on slf7 for e20:prof -- details available through the CI dashboard

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[FNALbuild]

⚠️ CI build for SBND Warning at phase ci_tests SBND on slf7 for e20:prof -- details available through the CI dashboard

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[FNALbuild]

⚠️ CI build for SBND Warning at phase ci_tests SBND on slf7 for c7:prof -- details available through the CI dashboard

🚨 For more details about the warning phase, check the ci_tests SBND phase logs

parent CI build details are available through the CI dashboard

[jedori0228]

@miquelnebot This PR should be merged to follow the updates made in SBNSoftware/icaruscode#612.