ROX-31478: Implement list clusters tool

[mtodor]

Description

This PR is adding implementation of list clusters tool.

Input parameters support offset and limit. Unfortunately StackRox API does not support paging for /v1/clusters endpoint. So paging is done on a client side within the MCP server.

For validation we are using JSON schema. Defining schema is not ideal, so the processes that schema is defined from struct with additional configuration of defaults and validation values.

Validation

• Build and test it against demo staging with MCP inspector
• Test with LLM

[codecov-commenter]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
193	2	191	0

View the full list of 2 ❄️ flaky test(s)

github.com/stackrox/stackrox-mcp/internal/testutil::

Flake rate in main: 100.00% (Passed 0 times, Failed 2 times)

Stack Traces | 0s run time

Build error

github.com/stackrox/stackrox-mcp/internal/toolsets/mock::

Flake rate in main: 100.00% (Passed 0 times, Failed 2 times)

Stack Traces | 0s run time

Build error

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