8344159: Add lint warnings for unnecessary warning suppression

[archiecobbs]

This PR adds a new Lint category "suppression" and associated warnings for @SuppressWarnings annotations that are unnecessary because they don't actually suppress any warnings.

Summary of changes:

• Add a new lint category "suppression" (disabled by default) and an associated warning for @SuppressWarnings annotations that don't actually suppress any warnings.
• Update the LintMapper to keep track of which @SuppressWarnings suppressions have been validated¹ and (later) generate warnings about those that never were.
• Update Log.warning() so it automatically validates any current suppression of the warning's lint category in effect.
• Augment Lint.isEnabled() and Lint.isSuppressed() with a new boolean validate parameter that specifies whether to also validate any current suppression.
• Add new method Lint.isActive() to check whether a category is enabled or suppression of the category is being tracked - in other words, the calculation for the warning needs to be performed. This is used when the calculation of a warning is non-trivial, making it worthwhile to check whether that calculation is needed.
• Update *.gmk build files to add -Xlint:-suppression flags so that the build doesn't break (the JDK itself contains hundreds of unnecessary @SuppressWarnings annotations).

¹ The suppression of a lint category is "validated" as soon as it suppresses some warning in that category

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8356043 to be approved

Issues

• JDK-8344159: Add lint warnings for unnecessary warning suppression (Enhancement - P4)
• JDK-6723459: Compiler should flag where warning suppression is not required (Enhancement - P3)
• JDK-8356043: Add lint warnings for unnecessary warning suppression (CSR)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/25167/head:pull/25167
$ git checkout pull/25167

Update a local copy of the PR:
$ git checkout pull/25167
$ git pull https://git.openjdk.org/jdk.git pull/25167/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 25167

View PR using the GUI difftool:
$ git pr show -t 25167

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/25167.diff

[archiecobbs]

/touch

[openjdk]

@archiecobbs The pull request is being re-evaluated and the inactivity timeout has been reset.

[archiecobbs]

/label remove hotspot-jfr

[openjdk]

@archiecobbs
The hotspot-jfr label was successfully removed.

[archiecobbs]

/label remove kulla

[openjdk]

@archiecobbs
The label kulla is not a valid label.
These labels are valid:

• graal
• serviceability
• hotspot
• hotspot-compiler
• ide-support
• i18n
• shenandoah
• jdk
• javadoc
• security
• hotspot-runtime
• jmx
• build
• nio
• client
• core-libs
• compiler
• net
• hotspot-gc
• hotspot-jfr