chore(web): stringify label text

[airslice]

Overview

When use expression to set label text we get values from feature property and the value could be number.
When pass number to LabelGraphics text, cesium will throw out error.

What I've done

What I haven't done

How I tested

Which point I want you to review particularly

Memo

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[codecov]

Codecov Report

Merging #848 (42e2247) into main (7aa3463) will increase coverage by 0.00%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #848   +/-   ##
=======================================
  Coverage   25.61%   25.61%           
=======================================
  Files        1644     1644           
  Lines      180743   180745    +2     
  Branches     3919     3920    +1     
=======================================
+ Hits        46298    46301    +3     
+ Misses     133356   133355    -1     
  Partials     1089     1089           

Flag	Coverage Δ
web	23.82% <0.00%> (+<0.01%)	⬆️
web-beta	23.82% <0.00%> (+<0.01%)	⬆️
web-classic	23.82% <0.00%> (+<0.01%)	⬆️
web-utils	23.82% <0.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...a/lib/core/engines/Cesium/Feature/Marker/index.tsx	13.77% <0.00%> (-0.13%)	⬇️

... and 2 files with indirect coverage changes