Performance improvements

[TheTeaCat]

• Updates the go shared lib to initialise the go middleware twice (once for request validation, once for response validation) and reuse them.
• Implements passing through the request and response headers so they appear in logs
• Removes hard-coded content-type of application/json so responses of other content-types can be validated
• Removes a bunch of unused fields in the filter context & increases clang-format line length from 80 to 120.