add IT to show a checker errors affects EFFECTIVELY_FINAL in subsequent source files

[XN137]

checkerBugGood passes and its output always shows flags like this:

sources files: /GenericException.java, /Violation.java, /SpecialException.java
message1 (effectivelyFinal: true, flags: 2207613190144)
args1 (effectivelyFinal: true, flags: 2224793059328)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
message2 (effectivelyFinal: true, flags: 2207613190144)
args2 (effectivelyFinal: true, flags: 2224793059328)
message2 (effectivelyFinal: true, flags: 2207613190144)

checkerBugBad1 fails with:

expected not to contain:
    : [FormatStringAnnotation]
but was:
    [/Violation.java:4: error: [UnusedVariable] The local variable 'x' is never read.
        int x = 0;
            ^
        (see https://errorprone.info/bugpattern/UnusedVariable)
      Did you mean to remove this line?, /SpecialException.java:6: error: [FormatStringAnnotation] All variables passed as @FormatString must be final or effectively final
        super(message2, args2);
             ^
        (see https://errorprone.info/bugpattern/FormatStringAnnotation)]

and output:

sources files: /GenericException.java, /Violation.java, /SpecialException.java
message1 (effectivelyFinal: true, flags: 2207613190144)
args1 (effectivelyFinal: true, flags: 2224793059328)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
message2 (effectivelyFinal: false, flags: 8589934592)
args2 (effectivelyFinal: false, flags: 25769803776)
message2 (effectivelyFinal: false, flags: 8589934592)

note how message1 from GenericException.java has the same flags as usual, but message2 from SpecialException.java is no longer effectively final... because it comes after Violation.java ?

checkerBugBad2 fails with output:

sources files: /Violation.java, /GenericException.java, /SpecialException.java
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
message1 (effectivelyFinal: false, flags: 8589934592)
args1 (effectivelyFinal: false, flags: 25769803776)
message2 (effectivelyFinal: false, flags: 8589934592)
args2 (effectivelyFinal: false, flags: 25769803776)
message2 (effectivelyFinal: false, flags: 8589934592)

note how now both message1 from GenericException.java and message2 from SpecialException.java are no longer effectively final... because they both come after Violation.java ?

checkerBugBad3 fails with output:

sources files: /Violation.java, /SpecialException.java, /GenericException.java
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
x (effectivelyFinal: true, flags: 2199023517696)
message2 (effectivelyFinal: false, flags: 8589934592)
args2 (effectivelyFinal: false, flags: 25769803776)
message2 (effectivelyFinal: false, flags: 8589934592)
message1 (effectivelyFinal: false, flags: 8589934592)
args1 (effectivelyFinal: false, flags: 25769803776)

same flags as for checkerBugBad2

reproduced in jdks:

openjdk version "17.0.12" 2024-07-16 LTS
OpenJDK Runtime Environment Zulu17.52+17-CA (build 17.0.12+7-LTS)
OpenJDK 64-Bit Server VM Zulu17.52+17-CA (build 17.0.12+7-LTS, mixed mode, sharing)

and

openjdk version "21.0.4" 2024-07-16 LTS
OpenJDK Runtime Environment Zulu21.36+17-CA (build 21.0.4+7-LTS)
OpenJDK 64-Bit Server VM Zulu21.36+17-CA (build 21.0.4+7-LTS, mixed mode, sharing)