Feature: support configurable pager for sdk list output #401

When implementing the list subcommand in Rust, support a configurable pager so users can control how output is displayed.

Currently the bash implementation pipes sdk list output through a pager (defaulting to less). Users can work around this with PAGER=cat sdk list java, but there is no persistent config option.

Proposed behaviour

• Respect the PAGER environment variable (as most Unix tools do)
• Optionally expose a sdkman_pager config key in ~/.sdkman/etc/config to set a persistent default (e.g. sdkman_pager=cat to disable paging)

Related

• sdkman-cli #515 (closed — configurable pager request in bash CLI)