front: review length field on editor

[sim51]

fix #7489

On the editor, the length field directly impacts curves & slopes.

When changing from 10800 to 11000, you need to pass through the value 1 ,which trigger a re-computation of curves, and you lost all the data from 1 to 10800.

To avoid that, a debounce of 1.5sec has been set on this field, but it introduces a new bug : if you change the value and press enter in less than 1.5sec, the new value is not send to the backend.

So to fix those issues, this commit :

• put the length on the top of the form with a separator
• add a user validation mechanism via a button

The design has been done Thibaut.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 72 lines in your changes are missing coverage. Please review.

Project coverage is 29.34%. Comparing base (c4b205e) to head (0e35e2d).
Report is 1 commits behind head on dev.

Files	Patch %	Lines
...components/LinearMetadata/FormLineStringLength.tsx	0.00%	43 Missing and 1 partial ⚠️
.../trackEdition/components/TrackEditionLeftPanel.tsx	0.00%	26 Missing ⚠️
.../src/applications/editor/components/EditorForm.tsx	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #7510      +/-   ##
============================================
- Coverage     29.34%   29.34%   -0.01%     
  Complexity     2012     2012              
============================================
  Files          1197     1197              
  Lines        147058   147050       -8     
  Branches       2889     2889              
============================================
- Hits          43156    43152       -4     
+ Misses       102202   102198       -4     
  Partials       1700     1700              

Flag	Coverage Δ
core	75.07% <ø> (ø)
editoast	72.51% <ø> (-0.02%)	⬇️
front	9.76% <0.00%> (+<0.01%)	⬆️
gateway	2.41% <ø> (ø)
railjson_generator	87.49% <ø> (ø)
tests	84.23% <ø> (ø)

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[SharglutDev]

Thank you for this PR and the nice comment history in the issue.

Left just a syntax comment.

And regarding your comments in the issue, it seems we can still press "enter" in the length field, resulting to saving the form with an empty payload.

[SharglutDev]

Lgtm and tested. Thank your for the changes :)