RFR: 8198551 - Rename hotspot_tier1 test group to tier1

[Christian Tornqvist]

Please review this small change that renames the hotspot_tier1 test group to tier1 in order to match the naming definition of langtools, jdk, jaxp and nashorn. This enables the use of run-test to run all of the tier1 tests locally:

make run-test-tier1
Building target 'run-test-tier1' in configuration 'macosx-x64'
warning: no debug symbols in executable (-arch x86_64)
warning: no debug symbols in executable (-arch x86_64)
Test selection 'tier1', will run:
* jtreg:open/test/hotspot/jtreg:tier1
* jtreg:open/test/jdk:tier1
* jtreg:open/test/langtools:tier1
* jtreg:open/test/nashorn:tier1
* jtreg:open/test/jaxp:tier1

The jdk_svc_sanity test group is part of the Hotspot tier1 definitions but not part of the Hotspot test root, so I moved that group into jdk:tier1 

Webrev: http://cr.openjdk.java.net/~ctornqvi/webrev/8198551/webrev.00/ <http://cr.openjdk.java.net/~ctornqvi/webrev/8198551/webrev.00/>
Bug: https://bugs.openjdk.java.net/browse/JDK-8198551 <https://bugs.openjdk.java.net/browse/JDK-8198551>

Thanks,
Christian