Revert "allocator: zero limit in SetExiting for backward compatibility"

This reverts commit a070522.

Allocator deployments going forward must first have been running release
v0.102.0 prior to deploying on this commit.

allocator: zero limit in SetExiting for backward compatibility

When deploying to existing clusters, old allocators don't understand the Exiting
field and need to see a zeroed limit to drain items from exiting members. Revert
this commit once the cluster is fully upgraded.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

update all dependencies to latest versions

Code changes to accommodate API updates:
- Fixed tablewriter API: SetHeader() -> Header()
- Fixed gRPC balancer test mocks to work with v1.73+ requirements
  by using wrapper pattern instead of direct interface implementation
- Simplified test structures by removing unnecessary wrapper layer
- Fixed some incorrect usages of legacy `errors` package.

update etcd dependency

This pulls in the fix for an issue that could cause the etcd client to use an
incorrect revision when re-starting a watch after an etcd server failure. This
presented as a crash in production due to receiving a watch event with a
revision equal to (not greater) than the last processed revision. It was
difficult to follow the discussion in the etcd issues, but this comment sums it
up nicely:
etcd-io/etcd#15248 (comment)

build(deps): bump golang.org/x/net from 0.17.0 to 0.23.0

Bumps [golang.org/x/net](https://github.com/golang/net) from 0.17.0 to 0.23.0.
- [Commits](golang/net@v0.17.0...v0.23.0)

---
updated-dependencies:
- dependency-name: golang.org/x/net
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

changelog: update ahead of v0.89 release

update changelog in preparation for 0.88.0 release (#277)

update CHANGELOG for v0.87.3

update CHANGELOG ahead of v0.87.2

update CHANGELOG ahead of v0.87