Update version to 54.2.0 and add CHANGELOG

[alamb]

Which issue does this PR close?

• Part of Release arrow-rs / parquet minor version 54.2.0 (~Mar~ Feb 2025) #7083

Rationale for this change

What changes are included in this PR?

1. Update version
2. Update changelog

Are there any user-facing changes?

[tustvold]

I wonder if we can get #7122 to this release, to avoid changing the docs only to change the behaviour back - see #7122 (comment)

[alamb]

I wonder if we can get #7122 to this release, to avoid changing the docs only to change the behaviour back - see #7122 (comment)

Sure -- no problem

Update:

• fix: NullBufferBuilder::allocated_size should return Size in Bytes #7122 is merged