Support resource patterns in @TestPropertySource locations

Inspired by the recently added support for resource patterns in
@PropertySource locations, this commit adds the same support for
resource locations in @TestPropertySource.

For example, assuming the `config` folder in the classpath contains
only 3 files matching the pattern `file?.properties`,

... the following:

@TestPropertySource("classpath:/config/file1.properties")
@TestPropertySource("classpath:/config/file2.properties")
@TestPropertySource("classpath:/config/file3.properties")

... or:

@TestPropertySource({
    "classpath:/config/file1.properties",
    "classpath:/config/file2.properties",
    "classpath:/config/file3.properties"
})

... can now be replaced by:

@TestPropertySource("classpath*:/config/file?.properties")

See gh-21325
Closes gh-31055

framework-docs/modules/ROOT/pages/testing/testcontext-framework/ctx-management/property-sources.adoc

@@ -37,9 +37,12 @@ Each path is interpreted as a Spring `Resource`. A plain path (for example,
 in which the test class is defined. A path starting with a slash is treated as an
 absolute classpath resource (for example: `"/org/example/test.xml"`). A path that
 references a URL (for example, a path prefixed with `classpath:`, `file:`, or `http:`) is
-loaded by using the specified resource protocol. Resource location wildcards (such as
-`{asterisk}{asterisk}/{asterisk}.properties`) are not permitted: Each location must
-evaluate to exactly one properties resource.
+loaded by using the specified resource protocol.
+
+Property placeholders in paths (such as `${...}`) will be resolved against the `Environment`.
+
+As of Spring Framework 6.1, resource location patterns are also supported — for
+example, `"classpath*:/config/*.properties"`.
 
 The following example uses a test properties file: