Impossible to use the virtual column generated by the timestamp index ($ts$DAY) in the startree index

When I try to create my realtime table with a timestamp and a startree index, I get this error :

`Invalid table config: my-table-name_REALTIME. Column Name $ts$DAY defined in StarTreeIndex Config must be a valid column defined in the schema`

Currently the table config validation requires all the star-tree index to be explicitly configured within the schema.

Start by reproducing realtime table creation with a timestamp column and a StarTree index using the virtual $ts$DAY column. Read the table config validation and StarTreeIndex configuration handling; done means the configuration is accepted without requiring $ts$DAY to be explicitly declared in the schema.

Written by the indexing model from the issue text.