Temperature can be given as float or sp.Expr

[RemDelaporteMathurin]

Proposed changes

This fixes #741 by adding a setter/getter to the T attribute of Simulation.

Now, users can simply give the temperature as a numerical value or sympy Expression without having to create a Temperature object.

Little QoL improvement!

Types of changes

What types of changes does your code introduce to FESTIM?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• Black formatted
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.52%. Comparing base (fb2c99f) to head (6cb7559).
Report is 196 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #770   +/-   ##
=======================================
  Coverage   99.51%   99.52%           
=======================================
  Files          58       58           
  Lines        2488     2501   +13     
=======================================
+ Hits         2476     2489   +13     
  Misses         12       12           

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[KulaginVladimir]

Possibly, an else case with an error can be included to add clarity? Similar to

FESTIM/festim/generic_simulation.py

Lines 124 to 127 in fb2c99f

	else:
	raise TypeError(
	"Accepted types for traps are list, festim.Traps or festim.Trap"
	)

[RemDelaporteMathurin]

added