Bump module serialization version

[webmaster128]

• Bump module serialization version due to Wasmer upgrade in 1.4 -> 1.5. We were warned by the Wasmer team long time ago that we should not expect module compatibility across Wasmer versions.
• Let's add a .module file extension to the module files to make it easier for node operators to reason about those things

[chipshort]

Isn't the cache invalidated already since the wasmer module version increased?

[webmaster128]

Isn't the cache invalidated already since the wasmer module version increased?

In theory this should always bee there case. Seems like it worked here. But we also has cases in the past in which the automatic bumping did not work but the modules were still incompatible. By bumping our version, we are on the safe side.