CI Fix to Prevent Checks Dealing with Large Array Sizes

[aidancch]

What changes were proposed in this pull request?

Updating SnappyTest.java and ignoring checks with arrays of large sizes.

Why are the changes needed?

To prevent java.lang.OutOfMemory errors from being caught during GitHub checks.

How was this patch tested?

SnappyTest.java

[xerial]

Extract this as a new function so that we don't need to repeat it

[xerial]

This part fails when CI env is not set:

[error] Caused by: java.lang.NullPointerException: Cannot invoke "String.equals(Object)" because the return value of "java.lang.System.getenv(String)" is null
[error]     at org.xerial.snappy.SnappyTest.isTooLargeFloatArrayInputLengthForBitShuffleShuffle(SnappyTest.java:490)
[error]     at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error]     at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
[error]     at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error]     at java.lang.reflect.Method.invoke(Method.java:568)

Need to add a null-value check for the getenv result

[xerial]

@aidanchiu1112 GitHub Actions will set CI=true (CI=false will never be set), so the condition should be fixed accordingly.

For example:

        Assume.assumeFalse("Skipped on CI", System.getenv("CI").equals("true"));

[xerial]

Thanks for the fix. It looks good to me now. I'll merge it.