Kibana: [APM] Add additional keywords to select legend colour in RPM/TPM graph

[formgeist]

We're already translating transaction.result HTTP 2xx, 3xx, 4xx and 5xx to a specific palette in the RPM graph. We could extend this to select colours for positive or negative keywords such as;

Green (teal): ok, success
Red (magenta): failure, fail and error

Keywords should be case-insensitive so doesn't matter if they're camel-, lower- or uppercase.

[formgeist]

@elastic/apm-agent-devs Prepping this for implementation, would be great to get some more keywords we might want to trigger a specific colour in the palette of status codes. Thoughts?

[mikker]

The ones listed already are 👌

Green (teal): ok, success
Red (magenta): failure, fail and error

[beniwohli]

Agreed, I don't think we need to provide a whole bunch of aliases for this.

would be great if they were case insensitive, though