feat: improve support for sqlite named parameters

[orisano]

sqlite supports the named parameter, but currently sqlc does not rewrite it as it does in postgresql.
Because named.IsParamSign judges whether named parameter is named or not by the content of ast.A_Expr, but sqlite3 converts from BindContext to ast.ParamRef and loses the name information.
In sqlite3, it is modified to return ast.A_Expr or ast.ParamRef depending on the contents of BindContext when converting.

And, parameter functions do not work in sqlite.
This is because names containing a dot, such as sqlc.arg, cause a syntax error.
So functions starting with sqlc_ are interpreted as starting with sqlc. in sqlite.

related:

• sqlc.narg does not work for sqlite3 #1881
• feat(sqlite) adding support for nullable types #2157

[kyleconroy]

Closed via #2274