Refactor filter configuration to make the different test server filte…

…rs independent (#855)

This is a followup to #852. In that change, we duplicated ResponseOptions onto separate DynamicDelayConfiguration and TimeTrackingConfiguration protos. However, this resulted in many fields on those protos that were not relevant to each filter. In this PR, we make it so that only the relevant fields exist on each proto.

Resulting changes:
1. Moved DynamicDelayConfiguration and TimeTrackingConfiguration into their own files, and moved their fields into those protos directly.
2. In order to make request headers still work, there is now manual logic for taking in a ResponseOptions proto via json and cherrypicking the fields relevant to each filter.
3. The generic method computeEffectiveConfiguration was moved to each filter's anonymous namespace.
4. All configs, tests, and markdown files updated to use the new protos.
5. Some tests have been removed that are no longer necessary, or never provided additional coverage, including some that are less feasible now.
    - HeaderMerge was removed, but everything it tested for was moved into new unit tests of MergeJsonConfig.

Signed-off-by: Nathan Perry <[email protected]>

Update Envoy to 84b6682 (May 23, 2022) (#856)

- Envoy's `.bazelrc` reordered the tools paths on macOS
- `Envoy::Http::Http1::ActiveClient` 1-arg constructor was removed; migrated to the 2-arg constructor with the second arg `absl::nullopt` 

Signed-off-by: eric846 <[email protected]>

Release notes for v0.2 + doc update (#100)

Signed-off-by: Otto van der Schaaf <[email protected]>

Update README.md & tagline consistency update (#79)

Signed-off-by: Otto van der Schaaf <[email protected]>