Use the EmitDefaultValues field for the namespace capacity get command

[khisakuni]

What was changed

Adds and wires up a EmitDefaultValues option when printing resources. Only the namespace capacity get command currently uses it.

Depends on temporalio/api-go#306

Why?

The namespace capacity get command has some fields that are useful to print when the response from the API has zero values. For example
before:

Namespace        my.namespace
  CurrentCapacity  {"onDemand":{},"latestRequest":{...}}
  ModeOptions      {"provisioned":{"validTruValues":[2,3,4,6,8,10,12],"maxAvailableTruValue":4},"onDemand":{"apsLimit":500}}
  Stats            {"aps":{}}

after:

Namespace        my.namespace
  HasLegacyLimits  false
  CurrentCapacity  {"onDemand":{},"latestRequest":{...}}
  ModeOptions      {"provisioned":{"validTruValues":[2,3,4,6,8,10,12],"maxAvailableTruValue":4},"onDemand":{"apsLimit":500}}
  Stats            {"aps":{"mean":0,"p90":0,"p99":0}}

The HasLegacyLimits is displayed and the Stats field is meaningful now.

Checklist

1. Closes

2. How was this tested:

3. Any docs updates needed?

---

Note

Low Risk
Opt-in printer behavior change with default off, so existing command output is unchanged; only capacity get opts in. Shared printer plumbing is touched but behavior remains backward compatible.

Overview
Makes zero-valued fields visible in namespace capacity get output (e.g. HasLegacyLimits: false, zeroed stats), so capacity info is more useful when the API returns defaults.

Adds an opt-in EmitDefaultValues flag to the shared printer (PrintResourceOptions / StructuredOptions). When set, scalar defaults are printed in both text and JSON; unset pointer/message fields stay omitted. Only the capacity get command enables it today.

Also bumps go.temporal.io/api for CustomJSONMarshalOptions.EmitDefaultValues support, and extends test helpers accordingly.

^{Reviewed by Cursor Bugbot for commit 3251c8e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

^{Reviewed by Cursor Bugbot for commit 2a9b293. Configure here.}