[DRAFT] chore: improve system tests

[daniel-sanche]

The system tests in #18013 were running for 3 hours before timing out. This PR touches the same packages, to experiment at ways to improve reliability for the next release

[gemini-code-assist]

Code Review

This pull request increases the Kokoro build timeout to 6 hours and introduces a per-package timeout mechanism (defaulting to 35 minutes) using the timeout command in .kokoro/system.sh. It also adds tracking and reporting for timed-out packages, and triggers system tests across multiple packages. The reviewer feedback recommends declaring the pkg and timed_out variables as local at the top of the reap_parallel_results function in .kokoro/system.sh to prevent global namespace pollution and duplicate declarations.

[gemini-code-assist]

To prevent global namespace pollution and avoid duplicate local declarations, declare pkg and timed_out as local variables at the top of the reap_parallel_results function.

Suggested change

	local retval=0
	local failed_count=0
	local timed_out_count=0
	local succeeded_count=0
	local retval=0
	local failed_count=0
	local timed_out_count=0
	local succeeded_count=0
	local pkg
	local timed_out

[gemini-code-assist]

Remove the local keyword here since pkg is now declared at the top of the function.

Suggested change

	local pkg=$(basename "$failed" .failed)
	pkg=$(basename "$failed" .failed)

[gemini-code-assist]

Remove the local keyword here since pkg is now declared at the top of the function.

Suggested change

	local pkg=$(basename "$failed" .failed)
	pkg=$(basename "$failed" .failed)