Consider supporting character encodings other than utf-8

### TL;DR

Currently actions like `string_replace` and `regex_replace` assume that the files they are operating on are utf-8 encoded. We could consider making this more flexible.

### Detailed design

_No response_

### Alternatives considered

_No response_

### Additional information

_No response_

Look at the `string_replace` and `regex_replace` actions in the codebase to understand how they currently handle file encoding. Investigate Go's encoding packages (like `golang.org/x/text/encoding`) to see how to detect and convert different character encodings. Determine what 'done' looks like by checking if there are existing tests for these actions that would need to be updated for new encoding support.

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