feat(spectre): add isource (current source)

[rahulk29]

Adds support for the Spectre isource component.
Positive current is drawn from the p terminal
and enters the n terminal.

[codecov]

Codecov Report

Attention: 47 lines in your changes are missing coverage. Please review.

Comparison is base (cad8c96) 40.68% compared to head (6799144) 40.64%.

Files	Patch %	Lines
tools/spectre/src/blocks.rs	0.00%	47 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #369      +/-   ##
==========================================
- Coverage   40.68%   40.64%   -0.05%     
==========================================
  Files         167      167              
  Lines       21275    21322      +47     
  Branches     8942     8963      +21     
==========================================
+ Hits         8656     8666      +10     
- Misses       6703     6742      +39     
+ Partials     5916     5914       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.