sqlite: make sourceSQL and expandedSQL string-valued properties

Change sourceSQL and expandedSQL from being methods to being
string-valued properties. These fields

- are conceptually properties (and not actions),
- are derived deterministically from the current state of the object,
- require no parameters, and
- are inexpensive to compute.

Also, following the naming conventions of ECMAScript for new features,
most function names should usually contain a verb, whereas names of
(dynamically computed) properties generally should not, so the current
names also seem more appropriate for properties than for functions.

PR-URL: https://github.com/nodejs/node/pull/54721
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/sqlite.md

@@ -194,17 +194,17 @@ objects. If the prepared statement does not return any results, this method
 returns an empty array. The prepared statement [parameters are bound][] using
 the values in `namedParameters` and `anonymousParameters`.
 
-### `statement.expandedSQL()`
+### `statement.expandedSQL`
 
 <!-- YAML
 added: v22.5.0
 -->
 
-* Returns: {string} The source SQL expanded to include parameter values.
+* {string} The source SQL expanded to include parameter values.
 
-This method returns the source SQL of the prepared statement with parameter
+The source SQL text of the prepared statement with parameter
 placeholders replaced by the values that were used during the most recent
-execution of this prepared statement. This method is a wrapper around
+execution of this prepared statement. This property is a wrapper around
 [`sqlite3_expanded_sql()`][].
 
 ### `statement.get([namedParameters][, ...anonymousParameters])`
@@ -293,15 +293,15 @@ be used to read `INTEGER` data using JavaScript `BigInt`s. This method has no
 impact on database write operations where numbers and `BigInt`s are both
 supported at all times.
 
-### `statement.sourceSQL()`
+### `statement.sourceSQL`
 
 <!-- YAML
 added: v22.5.0
 -->
 
-* Returns: {string} The source SQL used to create this prepared statement.
+* {string} The source SQL used to create this prepared statement.
 
-This method returns the source SQL of the prepared statement. This method is a
+The source SQL text of the prepared statement. This property is a
 wrapper around [`sqlite3_sql()`][].
 
 ### Type conversion between JavaScript and SQLite