ci: configure actions/setup-java maven caching across workflows to fix 429 Too many requests flakiness - #14044

…x 429 flakiness

Enable 'cache: maven' in 'actions/setup-java' across 27 GitHub Actions workflows to eliminate redundant dependency downloads and mitigate HTTP 429 (Too Many Requests) rate limiting errors from Maven Central.

Remove fragile and deprecated week-of-year date steps and custom actions/cache configs that conflicted with native setup-java caching.

Error logs observed prior to fix:
```
18:31:58:640 [ERROR] Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:3.6.0:check (checkstyle) on project gax-bom: Execution checkstyle of goal org.apache.maven.plugins:maven-checkstyle-plugin:3.6.0:check failed: Plugin org.apache.maven.plugins:maven-checkstyle-plugin:3.6.0 or one of its dependencies could not be resolved:
18:31:58:640 [ERROR] 	Failed to read artifact descriptor for org.iq80.snappy:snappy:jar:0.4
...
18:33:16:682 [ERROR] The project com.google.api:gax-bom:2.84.0-SNAPSHOT (/home/runner/work/google-cloud-java/google-cloud-java/sdk-platform-java/gax-java/gax-bom/pom.xml) has 1 error
18:33:16:682 [ERROR] Non-resolvable parent POM for com.google.api:gax-bom:2.84.0-SNAPSHOT: The following artifacts could not be resolved: com.google.cloud:google-cloud-shared-config:pom:1.17.0 (absent): com.google.cloud:google-cloud-shared-config:pom:1.17.0 failed to transfer from https://repo.maven.apache.org/maven2 during a previous attempt. This failure was cached in the local repository and resolution is not reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact com.google.cloud:google-cloud-shared-config:pom:1.17.0 from/to central (https://repo.maven.apache.org/maven2): status code: 429, reason phrase: Too Many Requests (429) and 'parent.relativePath' points at no local POM @ line 11, column 11 -> [Help 2]
```