feat: add manager ready timeout setting (experimental)

[eleanorjboyd]

add experimental setting allowing the user to control how long the manager timeout is (ie how long to wait for managers to register or attempt to register environments they discover)

[Copilot]

Pull request overview

Adds an experimental configuration setting to control how long the extension waits for environment/package managers to register before timing out, improving behavior on slower systems (e.g., remote or network filesystems).

Changes:

• Introduces python-envs.experimental.managerReadyTimeout (seconds) with a 5–120s allowed range.
• Updates manager registration wait logic to use the configured timeout value and logs the effective value on timeout.
• Adds corresponding configuration metadata and localized setting description.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/features/common/managerReady.ts	Reads the new setting and uses it to compute the timeout applied to manager readiness waits.
package.json	Contributes the new experimental setting with schema validation (default/min/max, machine scope).
package.nls.json	Adds the localized description string used by the new setting.