[release test] move release_tests.json upload into custom_image_build_and_test_init

[andrew-anyscale]

Follow-up to the chunked release_tests.json upload: have custom_image_build_and_test_init itself call buildkite-agent pipeline upload for each chunk it writes, gated behind a new --upload-to-buildkite flag. The bash init script drops its while loop and just passes the flag through.

Topic: upload-chunks-from-python
Signed-off-by: andrew andrew@anyscale.com

[andrew-anyscale]

Reviews in this chain:
└#62737 [release test] move release_tests.json upload into custom_image_build_and_test_init

[andrew-anyscale]

#	head	base	diff	date	summary
0	14b38dfc	4b679292	diff	Apr 17 14:40 PM	3 files changed, 74 insertions(+), 14 deletions(-)
1	3f5dda34	15f109b5	diff	Apr 17 15:11 PM	2 files changed, 16 insertions(+)
2	1ee32b93	743d06d5	diff	Apr 17 17:12 PM	0 files changed
3	238660a7	743d06d5	diff	Apr 17 17:13 PM	1 file changed, 1 insertion(+), 1 deletion(-)
4	a83341d5	c33b6074	diff	Apr 20 7:55 AM	1 file changed, 7 insertions(+)
5	46294fdb	30482d19	diff	Apr 21 8:47 AM	0 files changed

[gemini-code-assist]

Code Review

This pull request refactors the Buildkite pipeline upload process by moving the logic from a shell script into the Python initialization script. It introduces a new --upload-to-buildkite flag in custom_image_build_and_test_init.py, which uses the subprocess module to upload chunked test job files directly. Additionally, a new test case has been added to verify that the upload command is correctly invoked when the flag is enabled. I have no feedback to provide.

[aslonnie]

merge conflict?