evm: consistent error message names

[gabrocheleau]

This PR:

• Makes the EVMErrorMessage singular (EVMErrorMessages -> EVMErrorMessage)
• Renames EOFError to EOFErrorMessage to be consistnet with the above.

The convention would then be:

• Error messages live under an enum-like const/type that is named XYZErrorMessage
• Error classes or wrappers are named XYZError (e.g. EVMError)
• These error classes may have a message property that is then typed as XYZErrorMessage

[codecov]

Codecov Report

Attention: Patch coverage is 55.62130% with 75 lines in your changes missing coverage. Please review.

Project coverage is 79.55%. Comparing base (47529d0) to head (4f7f26d).
Report is 5 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
block	84.33% <ø> (ø)
blockchain	89.32% <ø> (ø)
client	67.99% <ø> (ø)
common	97.51% <ø> (ø)
devp2p	86.71% <ø> (-0.08%)	⬇️
evm	73.11% <55.62%> (-0.02%)	⬇️
mpt	89.74% <ø> (ø)
statemanager	69.06% <ø> (ø)
static	99.11% <ø> (ø)
tx	90.59% <ø> (ø)
util	89.36% <ø> (ø)
vm	55.50% <ø> (ø)

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[holgerd77]

LGTM