fix: bound the size a compressed payload may expand to (#3502)

[pjfanning]

cherry pick #3502

Motivation:
Five serializers gzip their payload and decompress it on the way back in, each with the same unbounded loop: read the whole GZIPInputStream into a ByteArrayOutputStream. gzip expands by up to about three orders of magnitude, so neither the size of the compressed bytes nor the transport's frame limit bounds the buffer the decompressed bytes are read into.

Modification:
Add Decompression (@internalapi) with a gunzip that stops once the decompressed size passes pekko.serialization.max-decompressed-size (default 256 MiB) and reports it as a NotSerializableException, and route all twelve call sites through it. The Jackson serializers already bound decompression and keep their own
pekko.serialization.jackson.compression.max-decompressed-size.

Result:
An over-expanding payload is rejected as an ordinary serialization failure. No behaviour change for payloads within the limit.

• change the default max-decompressed-size to unlimited

Motivation:
A bounded default could reject a payload an existing cluster legitimately exchanges, so a patch release carrying a 256 MiB default could break running clusters on upgrade. The bound should be opt-in.

Modification:
Default pekko.serialization.max-decompressed-size to -1, meaning no limit and matching the behaviour of earlier releases. A negative maximum skips the size check in gunzip. Config's getBytes refuses negative numbers, so the setting is read as a plain long first and as a memory size only when that is not a negative number.

Result:
Decompression is unbounded by default; configuring a size such as 256 MiB bounds it.

Tests:

• sbt "actor-tests/testOnly org.apache.pekko.serialization.DecompressionSpec" - 8 passed
• sbt "cluster/testOnly org.apache.pekko.cluster.protobuf.ClusterMessageSerializerDecompressionSpec" - 4 passed
• sbt "distributed-data/testOnly org.apache.pekko.cluster.ddata.protobuf.SerializationSupportDecompressionSpec" - 3 passed
• sbt "actor/scalafmtCheckAll" "actor-tests/scalafmtCheckAll" - clean

References:
Refs #3502

• also accept "unlimited" for max-decompressed-size

Motivation:
Review on #3515 noted that an explicit keyword is clearer than a magic number. Keep the two sibling settings consistent: accept both spellings here as well.

Modification:
pekko.serialization.max-decompressed-size reads "unlimited" or any negative number as no limit; the reference.conf default is written as unlimited. New tests cover the keyword default and an explicit -1.

Result:
max-decompressed-size = unlimited and = -1 both disable the bound.

Tests:

• sbt "actor-tests/testOnly org.apache.pekko.serialization.DecompressionSpec" - 9 passed
• sbt "actor/scalafmtCheckAll" "actor-tests/scalafmtCheckAll" - clean

References:
Refs #3515, Refs #3502