Update Runge-Kutta ODE solver

[oriolcg]

In this PR I modified the Runge-Kutta method in RungeKutta.jl to accommodate TransientFEOperators by adding a new operator type named TransientRungeKuttaFEOperator. This new type allows for a separate definition of the mass and right-hand side operators, as required by the Runge-Kutta scheme.

[codecov-commenter]

Codecov Report

Merging #919 (5963fff) into master (0b5dca3) will decrease coverage by 0.13%.
The diff coverage is 78.01%.

❗ Current head 5963fff differs from pull request most recent head 5d71179. Consider uploading reports for the commit 5d71179 to get more accurate results

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@@            Coverage Diff             @@
##           master     #919      +/-   ##
==========================================
- Coverage   88.44%   88.31%   -0.13%     
==========================================
  Files         191      174      -17     
  Lines       20652    20397     -255     
==========================================
- Hits        18266    18014     -252     
+ Misses       2386     2383       -3     

Files Changed	Coverage Δ
src/ODEs/ODETools/ODESolvers.jl	77.77% <ø> (ø)
src/ODEs/ODETools/ODETools.jl	100.00% <ø> (ø)
src/ODEs/ODETools/Tableaus.jl	63.44% <63.44%> (ø)
src/ODEs/TransientFETools/TransientFEOperators.jl	79.79% <66.96%> (-8.04%)	⬇️
src/ODEs/ODETools/RungeKutta.jl	84.84% <82.25%> (-9.32%)	⬇️
src/ODEs/ODETools/IMEXRungeKutta.jl	100.00% <100.00%> (ø)
src/ODEs/TransientFETools/ODEOperatorInterfaces.jl	100.00% <100.00%> (+6.34%)	⬆️

... and 40 files with indirect coverage changes

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[oriolcg]

Hi @santiagobadia, @fverdugo, @amartinhuertas, could any of you take a look at this PR? Thank you!

[fverdugo]

Hi @oriolcg!

I see that nothing critical outside the ODEs module was changed. So for me, looks good!

[JordiManyer]

Hi @oriolcg ,
Could you pull from master and log the changes in NEWS? I'll include these changes in the next release. Thanks!