[helm]support config override in starrocksFESpec/starrocksBeSpec/starrocksCnSpec

[mingmxu]

Describe the current behavior

Currently all the config in starrocks helm chart are taken as a block, see the code here. As a result, partial update is not supported.

Describe the enhancement

Support partial update in values.yaml to simplify configuration changes.

Additional context

cc @dengliu @yandongxiao

[yandongxiao]

‌‌The "partial update" you mentioned refers to adding or updating some additional configurations in other values.yaml files on top of a certain base values.yaml configuration?

[mingmxu]

‌‌The "partial update" you mentioned refers to adding or updating some additional configurations in other values.yaml files on top of a certain base values.yaml configuration?

Yes,

[yandongxiao]

This is a bit challenging because the current type of config is a string. We need to parse this string in _helper, convert it into the format of a map, and finally merge it with the default values. I tried to write it, but failed.