Issue #496 Support maven.build.cache.skipSave as module-level property

[alascbio]

Fixes #496

Description

At the moment, the build cache extension supports maven.build.cache.skipCache as a module-level property in pom.xml,
allowing specific modules to skip cache lookup.
However, maven.build.cache.skipSave does not currently behave the same way: it can be set from the CLI, but not as a module-level property.
This creates an inconsistency in multi-module builds.

A concrete issue is that a module can be configured with:

<properties>
    <maven.build.cache.skipCache>true</maven.build.cache.skipCache>
</properties>

to avoid reading from the cache, while still writing new entries to the cache at the end of the build.
In practice, this means a module can be excluded from cache lookup but still update the cache, which is not always desirable.

Expected behavior

Support the following in module pom.xml:

<properties>
    <maven.build.cache.skipSave>true</maven.build.cache.skipSave>
</properties>

When set on a module, this property should prevent cache writes for that module,
while still allowing cache reads unless maven.build.cache.skipCache=true is also set.
This would make skipSave consistent with the existing module-level behavior of skipCache.

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