Improve error reporting for jsonpath .double() method

When jsonpath .double() method detects that numeric or string can't be
converted to double precision, it throws an error.  This commit makes these
errors explicitly express the reason of failure.

Discussion: https://postgr.es/m/CAPpHfdtqJtiSXkP7tOXez18NxhLUH_-75bL8%3DOce4Ki%2Bbv7V6Q%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Tom Lane
Backpatch-through: 12

src/backend/utils/adt/jsonpath_exec.c

@@ -1055,7 +1055,7 @@ executeItemOptUnwrapTarget(JsonPathExecContext *cxt, JsonPathItem *jsp,
 					if (have_error)
 						RETURN_ERROR(ereport(ERROR,
 											 (errcode(ERRCODE_NON_NUMERIC_SQL_JSON_ITEM),
-											  errmsg("jsonpath item method .%s() can only be applied to a numeric value",
+											  errmsg("numeric argument of jsonpath item method .%s() is out of range for type double precision",
 													 jspOperationName(jsp->type)))));
 					res = jperOk;
 				}
@@ -1076,7 +1076,7 @@ executeItemOptUnwrapTarget(JsonPathExecContext *cxt, JsonPathItem *jsp,
 					if (have_error || isinf(val))
 						RETURN_ERROR(ereport(ERROR,
 											 (errcode(ERRCODE_NON_NUMERIC_SQL_JSON_ITEM),
-											  errmsg("jsonpath item method .%s() can only be applied to a numeric value",
+											  errmsg("string argument of jsonpath item method .%s() is not a valid representation of a double precision number",
 													 jspOperationName(jsp->type)))));
 
 					jb = &jbv;

src/test/regress/expected/jsonb_jsonpath.out

@@ -1496,7 +1496,9 @@ select jsonb_path_query('"1.23"', '$.double()');
 (1 row)
 
 select jsonb_path_query('"1.23aaa"', '$.double()');
-ERROR:  jsonpath item method .double() can only be applied to a numeric value
+ERROR:  string argument of jsonpath item method .double() is not a valid representation of a double precision number
+select jsonb_path_query('1e1000', '$.double()');
+ERROR:  numeric argument of jsonpath item method .double() is out of range for type double precision
 select jsonb_path_query('"nan"', '$.double()');
  jsonb_path_query 
 ------------------
@@ -1510,9 +1512,9 @@ select jsonb_path_query('"NaN"', '$.double()');
 (1 row)
 
 select jsonb_path_query('"inf"', '$.double()');
-ERROR:  jsonpath item method .double() can only be applied to a numeric value
+ERROR:  string argument of jsonpath item method .double() is not a valid representation of a double precision number
 select jsonb_path_query('"-inf"', '$.double()');
-ERROR:  jsonpath item method .double() can only be applied to a numeric value
+ERROR:  string argument of jsonpath item method .double() is not a valid representation of a double precision number
 select jsonb_path_query('"inf"', '$.double()', silent => true);
  jsonb_path_query 
 ------------------

src/test/regress/sql/jsonb_jsonpath.sql

@@ -312,6 +312,7 @@ select jsonb_path_query('{}', '$.double()', silent => true);
 select jsonb_path_query('1.23', '$.double()');
 select jsonb_path_query('"1.23"', '$.double()');
 select jsonb_path_query('"1.23aaa"', '$.double()');
+select jsonb_path_query('1e1000', '$.double()');
 select jsonb_path_query('"nan"', '$.double()');
 select jsonb_path_query('"NaN"', '$.double()');
 select jsonb_path_query('"inf"', '$.double()');