Fix unsupported language extensions in `plutus-tx`

Compiling the projects leads to various errors related to unsupported language extensions within `plutus-tx`. Now that these are actually reported by the plugin, we can fix them!

Start by compiling the projects that use `plutus-tx` and inspect the plugin's reports for unsupported language extensions. Trace those reports to the relevant `plutus-tx` configuration or source entry point; done means the reported unsupported extensions are fixed and the projects compile without those errors.

Written by the indexing model from the issue text.