Several components specify defaults instead of guesses

[avinashresearch1]

Describe the bug 🐞 Several components e.g., https://github.com/SciML/ModelingToolkitStandardLibrary.jl/blob/02a134cd430b035e43c8c43596d32ecbff1a08d5/src/Electrical/utils.jl#L35 https://github.com/SciML/ModelingToolkitStandardLibrary.jl/blob/02a134cd430b035e43c8c43596d32ecbff1a08d5/src/Electrical/utils.jl#L72 https://github.com/SciML/ModelingToolkitStandardLibrary.jl/blob/02a134cd430b035e43c8c43596d32ecbff1a08d5/src/Electrical/Analog/sensors.jl#L152 https://github.com/SciML/ModelingToolkitStandardLibrary.jl/blob/02a134cd430b035e43c8c43596d32ecbff1a08d5/src/Blocks/continuous.jl#L548 https://github.com/SciML/ModelingToolkitStandardLibrary.jl/blob/02a134cd430b035e43c8c43596d32ecbff1a08d5/src/Blocks/continuous.jl#L621

specify variables with defaults instead of guesses. Specifying a default in MTK v9 would mean that an explicit constraint is added to the initialization problem which often makes the problem infeasible or extremely overdetermined. This would be the equivalent of setting fix = true and specifying a start` value in Modelica.

[avinashresearch1]

https://github.com/SciML/ModelingToolkitStandardLibrary.jl/pull/281 fixes for some Thermal and Blocks components.