RFR: 8310815: Clarify the name of the main class, services and provider classes in module descriptor

[Mandy Chung]

Clarify the spec of `ModuleDescriptor::mainClass`, `ModuleDescriptor::uses`, `ModuleDescriptor.Provides::service` and `ModuleDescriptor.Provides::providers` to return a binary name. 

This PR also fixes JDK-8314449 to update the spec of `StackTraceElement::getClassName` and the `declaringClass` parameter of the constructor.

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Commit messages:
 - 8314449: Clarify the name of the declaring class of StackTraceElement
 - 8310815: Clarify the name of the main class, services and provider classes in module descriptor

Changes: https://git.openjdk.org/jdk/pull/15317/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15317&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310815
  Stats: 25 lines in 2 files changed: 3 ins; 4 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/15317.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15317/head:pull/15317

PR: https://git.openjdk.org/jdk/pull/15317