fix: 'append' in MeshRateLimit should be 'true' by default

[lobkovilya]

In Envoy if Append is not set then it's true by default:

Append
Should the value be appended? If true (default), the value is appended to existing values. Otherwise it replaces any existing values. This field is deprecated and please use append_action as replacement.

We already have this behavior in MeshHealthCheck.

Signed-off-by: Ilya Lobkov [email protected]

Checklist prior to review

• Link to docs PR or issue --
• Link to UI issue or PR --
• Is the issue worked on linked? --
• The PR does not hardcode values that might break projects that depend on kuma (e.g. "kumahq" as a image registry) --
• The PR will work for both Linux and Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
• Unit Tests --
• E2E Tests --
• Manual Universal Tests --
• Manual Kubernetes Tests --
• Do you need to update UPGRADE.md? --
• Does it need to be backported according to the backporting policy? --
• Do you need to explicitly set a > Changelog: entry here or add a ci/ label to run fewer/more tests?

Changelog: feat(policy): implement MeshRateLimit policy