[remote/downloader] Migrate Downloader to take Credentials

Progress on bazelbuild#15856

Closes bazelbuild#16601.

PiperOrigin-RevId: 485837451
Change-Id: I785882d0ff3e171dcaee6aa6f628bca9232c730a

Author: Yannic

src/main/java/com/google/devtools/build/lib/bazel/repository/downloader/DownloadManager.java

@@ -267,7 +267,7 @@ public Path download(
       try {
         downloader.download(
             rewrittenUrls,
-            credentialFactory.create(rewrittenAuthHeaders),
+            new StaticCredentials(rewrittenAuthHeaders),
             checksum,
             canonicalId,
             destination,
@@ -348,7 +348,7 @@ public byte[] downloadAndReadOneUrl(
     for (int attempt = 0; attempt <= retries; ++attempt) {
       try {
         return httpDownloader.downloadAndReadOneUrl(
-            rewrittenUrls.get(0), credentialFactory.create(authHeaders), eventHandler, clientEnv);
+            rewrittenUrls.get(0), new StaticCredentials(authHeaders), eventHandler, clientEnv);
       } catch (ContentLengthMismatchException e) {
         if (attempt == retries) {
           throw e;