[Flow EVM] add testnet chainID

[ramtinms]

closes #5459

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 55.80%. Comparing base (50761d4) to head (27372df).

Files	Patch %	Lines
fvm/evm/types/chainIDs.go	0.00%	8 Missing ⚠️
fvm/evm/types/emulator.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5527      +/-   ##
==========================================
- Coverage   55.82%   55.80%   -0.02%     
==========================================
  Files        1031     1031              
  Lines      100860   100862       +2     
==========================================
- Hits        56302    56290      -12     
- Misses      40229    40239      +10     
- Partials     4329     4333       +4     

Flag	Coverage Δ
unittests	55.80% <0.00%> (-0.02%)	⬇️

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[janezpodhostnik]

If we deploy this on top of an existing previewnet state, will that be ok?

[ramtinms]

The preview net is still the default one and also set to the same chain ID as before so should be safe.