doc(udf): merge udf docs for the same function

some UDFs may has mutiple doc string, each for different parameters type. The problem is for udf doc gen, it is unclear which doc string to publish in the generated doc (as the document only has one entry for each, it selects random one). Refer the PR #2734 .

know problem udfs
- ilike_match
- like_match
- regexp_like
- string
- substring
- or anything else you find

**Solution**

merge the multiple doc strings into single one, with all informations included. See how dayofyear implemented: https://github.com/4paradigm/OpenMLDB/blob/c1d5e1d4e810590e678d77294774832f0ad1a394/hybridse/src/udf/default_udf_library.cc#L2178-L2210

Look at the UDF definitions in hybridse/src/udf/default_udf_library.cc, starting with the listed functions (ilike_match, like_match, etc.). Compare with the dayofyear implementation to see how multiple doc strings are merged. The goal is to combine all parameter type variations into a single doc string for each function, ensuring the generated documentation includes all information.

Scritto dal modello di indicizzazione a partire dal testo della issue.