Operation request: Trim start/end matching a character

## Summary
Often I need to trim the start or end of a string, eg. to strip leading/trailing quotes or newlines. This doesn't seem to be an operation yet.

This can currently be roughly emulated with `Drop_bytes(0,1,false)Drop_bytes(-1,1,false)`, but this isn't as flexible.

### Example Input
`aaabbbccc`

### Example Output
When trimming text `a`: `bbbccc`
When trimming text `c`: `aaabbb`
When trimming regex `[a|c]{2}`: `abbbc`