Add a builder for ResourcesItemReader with support for specifying files via a pattern

[benelog]

Expected Behavior

A builder for ResourcesItemReader, consistent with the other readers and writers in the org.springframework.batch.infrastructure.item.file.builder package, that also supports specifying the resources with a file pattern:

ResourcesItemReader reader = new ResourcesItemReaderBuilder()
    .filesPattern("/data/inputs/*.csv")
    .name("resourcesReader")
    .build();

Current Behavior

ResourcesItemReader is the only reader in the org.springframework.batch.infrastructure.item.file package without a builder. It can only be configured through the default constructor and setResources(Resource[]).

Its Javadoc even suggests configuring it with a pattern ("Hint: use a pattern to configure."), which worked out of the box in XML configuration thanks to ResourceArrayPropertyEditor. In Java configuration, however, resolving the pattern is left to the user:

var resourcePatternResolver = new PathMatchingResourcePatternResolver();
ResourcesItemReader reader = new ResourcesItemReader();
reader.setResources(resourcePatternResolver.getResources("file:/data/inputs/*.csv"));
reader.setName("resourcesReader");

Context

This is a companion of #5056, which proposes the same pattern support for MultiResourceItemReaderBuilder (PR #5071). The proposed filesPattern(String) method follows the same naming and semantics, so the two builders would stay consistent.

I will submit a pull request for this shortly.

[benelog]

I have submitted a pull request for this: #5488