Fail fast on empty wasmvm cache metric setup (backport #1576)

[mergify]

This is an automatic backport of pull request #1576 done by Mergify.

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[codecov]

Codecov Report

Merging #1580 (7560319) into releases/v0.3x (390fda7) will increase coverage by 0.19%.
The diff coverage is 0.00%.

@@                Coverage Diff                 @@
##           releases/v0.3x    #1580      +/-   ##
==================================================
+ Coverage           57.96%   58.15%   +0.19%     
==================================================
  Files                  57       57              
  Lines                7603     7605       +2     
==================================================
+ Hits                 4407     4423      +16     
+ Misses               2885     2869      -16     
- Partials              311      313       +2     

Files Changed	Coverage Δ
x/wasm/keeper/metrics.go	50.00% <0.00%> (+50.00%)	⬆️

... and 2 files with indirect coverage changes