Handle safety analysis for this and super references

[carterkozak]

Before this PR

Previously we failed to handle safety metadata for this and super references similarly to other variable references. See the new tests for examples. Most notably, this meant one could implement a SafeLoggable exception thusly without a warning:

@Override
public String getLogMessage() {
    return getMessage(); // oh no! This is dangerous!
}

The danger is subtler than one might realize -- if such an exception is created with a known, safe message, it may be fine, however if it's constructed with a ctor that delegates to public Throwable(Throwable cause), then cause.toString() will be used as the exception message, which is almost certainly unsafe, even (or especially!) if the cause implements SafeLoggable due to the following:

public Throwable(Throwable cause) {
    fillInStackTrace();
    detailMessage = (cause==null ? null : cause.toString());
    this.cause = cause;
}

After this PR

==COMMIT_MSG==
Handle safety analysis for this and super references
==COMMIT_MSG==

[changelog-app]

Generate changelog in changelog/@unreleased

What do the change types mean?

• feature: A new feature of the service.
• improvement: An incremental improvement in the functionality or operation of the service.
• fix: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way.
• break: Has the potential to break consumers of this service's API, inclusive of both Palantir services
  and external consumers of the service's API (e.g. customer-written software or integrations).
• deprecation: Advertises the intention to remove service functionality without any change to the
  operation of the service itself.
• manualTask: Requires the possibility of manual intervention (running a script, eyeballing configuration,
  performing database surgery, ...) at the time of upgrade for it to succeed.
• migration: A fully automatic upgrade migration task with no engineer input required.

Note: only one type should be chosen.

How are new versions calculated?

• ❗The break and manual task changelog types will result in a major release!
• 🐛 The fix changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease.
• ✨ All others will result in a minor version release.

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Handle safety analysis for this and super references

Check the box to generate changelog(s)

• Generate changelog entry

[autorelease3]

Released 6.14.0