Find files on file system using a file pattern

To find traces programmatically in the file system where the source code (language server) is. For this I'd like to issue a command on a folder and search for file/directories with a given file pattern. For example:
"From a start directory, find all files with the file suffix *.log"
"From a start directory, find all directories that contains a file called metadata"

No file, test, or entry point is named in the issue. Start by locating the command or API that operates on a start directory, then trace how file-system queries are exposed. Done means supporting file-suffix searches and searches for directories containing a named file, with tests covering both examples.

Written by the indexing model from the issue text.