perf(kuma-cp): avoid rebuilding endpoint map

[jakubdyszkiewicz]

This PR removes rebuilding endpoint map in DataplaneProxyBuilder.
We already compute endpoint map for all data plane proxy in the mesh and cache it in MeshContext.
However, we were rebuilding the map in DataplaneProxyBuilder, because if we had no zone egress we decided if we want to include external service endpoints based on traffic permission. I changed the logic to only compute external services endpoint for each data plane proxy and share the endpoint map for the rest of services.

This saves a significant amount of CPU (2-3x when benchmarking with in-memory storage and mock Envoys)

Before:

After:

Fix #2989

Checklist prior to review

• Link to docs PR or issue -- no
• Link to UI issue or PR -- no
• Is the issue worked on linked? -- xDS proxy routing targets are mostly not used  #2989
• The PR does not hardcode values that might break projects that depend on kuma (e.g. "kumahq" as a image registry) -- no
• The PR will work for both Linux and Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS -- no
• Unit Tests --
• E2E Tests --
• Manual Universal Tests --
• Manual Kubernetes Tests --
• Do you need to update UPGRADE.md? -- no
• Does it need to be backported according to the backporting policy? -- no
• Do you need to explicitly set a > Changelog: entry here?

Changelog perf(kuma-cp): avoid rebuilding endpoint map

[lahabana]

That's a great perf improvement and also a nice code readability improvement :)