[FTheoryTools] Better type inference

[lgoettgens]

While looking at get_attribute uses all over Oscar, I found a lot of places in the FTheoryTools that could easily get enhanced by explicit type annotations.

Futhermore, I found some things around journal_name missing, which are added here. And I also included the change of euler_characteristic from QQFieldElem to Int from #4044 in here, as this might produce ugly conflicts otherwise.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.63%. Comparing base (629c37e) to head (17bf2a6).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4073      +/-   ##
==========================================
+ Coverage   84.17%   84.63%   +0.46%     
==========================================
  Files         600      600              
  Lines       82568    82622      +54     
==========================================
+ Hits        69503    69931     +428     
+ Misses      13065    12691     -374     

Files with missing lines	Coverage Δ
...heoryTools/src/AbstractFTheoryModels/attributes.jl	99.59% <100.00%> (+1.60%)	⬆️
...heoryTools/src/AbstractFTheoryModels/properties.jl	100.00% <100.00%> (+1.66%)	⬆️
.../FTheoryTools/src/HypersurfaceModels/attributes.jl	93.10% <100.00%> (ø)
...mental/FTheoryTools/src/TateModels/constructors.jl	97.46% <100.00%> (ø)
...FTheoryTools/src/WeierstrassModels/constructors.jl	95.65% <100.00%> (ø)

... and 40 files with indirect coverage changes

[HereAround]

Thank you very much @lgoettgens for catching and fixing all of this. Truly appreciated! Great!