support corner cases in SLO convertor function

[odubajDT]

Follow-up of #1760

Depends on #1976

Goal

The goal of this issue is to handle more complex corner cases in the SLO evaluation logic, that means interval ranges for the metric values. Definitions with a single criteria element with a single rule are already covered with #1955

Details

There are multiple options to be converted. There is a need to convert the use-cases that make logical sense and are common, but in some cases, where it is problematic and these cases will not be supported.

Criteria with 3 and more inputs won't be supported, only the first 2 non-percentage inputs (those not containing % as we do not support comparison rules) will be taken and converted. In the example below, only <600 and >400 rules will be converted. Rule >800 will be ignored.

objectives:
- sli: response_time_p95
  displayName: "Response Time P95"
  pass:
  - criteria
    - "<600"
    - ">400"
    - ">800"
  weight: 2
  key_sli: true

Secondly, support of conversion of multiple criteria elements won't be supported at all -> these criteria are combined with logical OR operator (see documentation here). Only a single criteria element rules will be supported. An example of unsupported SLOs for conversion here:

objectives:
- sli: response_time_p95
  displayName: "Response Time P95"
  pass:
  - criteria:
    - "<=+10%"
  - criteria
    - "<600"
  weight: 2
  key_sli: true

The buckets for rules with single criteria element but with one or more criteria combined with AND operator (see documentation here):

1. pass criteria set, warn criteria not set -> supported

objectives:
- sli: response_time_p95
  displayName: "Response Time P95"
  pass:
  - criteria:
    - ">400"
    - "<600"

2. pass criteria set, warn criteria set, warn criteria interval is superset of pass criteria interval -> supported

objectives:
- sli: response_time_p95
 displayName: "Response Time P95"
 pass:
 - criteria:
   - ">400"
   - "<600"
 warn:
 - criteria:
   - ">200"
   - "<800" 

3. pass criteria set, warn criteria set, pass criteria interval is superset of warn criteria interval -> supported

objectives:
- sli: response_time_p95
 displayName: "Response Time P95"
 pass:
 - criteria:
   - ">200"
   - "<800"
 warn:
 - criteria:
   - ">400"
   - "<600" 

4. pass criteria set, warn criteria set, pass criteria interval and warn criteria interval do not intercept -> unsupported

objectives:
- sli: response_time_p95
 displayName: "Response Time P95"
 pass:
 - criteria:
   - ">200"
   - "<400"
 warn:
 - criteria:
   - ">600"
   - "<800" 

DoD

• all the supported buckets options are able to be converted to AnalysisDefinition criteria logic
• unit tests
• usage of converter is documented together with corner-cases