Some small improvements prompted by PyLint errors

[pda]

PyLint was failing in CI on main after my recent changes:

************* Module buildkite_test_collector.collector.run_env
src/buildkite_test_collector/collector/run_env.py:11:0: R0903: Too few public methods (1/2) (too-few-public-methods)
************* Module buildkite_test_collector.collector.api
src/buildkite_test_collector/collector/api.py:21:0: C0301: Line too long (105/100) (line-too-long)
src/buildkite_test_collector/collector/api.py:11:0: R0903: Too few public methods (1/2) (too-few-public-methods)

I've avoided the long line by pulling out some env var name constants, which is nice anyway.

And I've disabled the very silly too-few-public-methods warning on the API and RunEnvBuilder classes. A constructor and one public method should be enough for anyone!

[Copilot]

Pull Request Overview

This PR addresses PyLint CI failures by fixing line length violations and disabling too-few-public-methods warnings on specific classes. The changes improve code maintainability by extracting environment variable names into constants and refactoring the API class to store configuration during initialization.

• Extracted environment variable names and default API URL into class constants
• Refactored API class to store token and API URL as instance variables during initialization
• Added pylint disable comments for too-few-public-methods and too-many-instance-attributes warnings

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/buildkite_test_collector/collector/run_env.py	Added pylint disable comments for code quality warnings
src/buildkite_test_collector/collector/api.py	Extracted constants and refactored API class initialization to store configuration