Avoid storing the whole BuildResult in StartupActionImpl

[gsmet]

The BuildResult contains references to all the build items, some of them contain references to class loaders or objects of significant size.

Note that it has value because StartupActionImpl is leaked as a reference of various non-static nested classes. I experimented with dropping the nested classes but it makes things harder to follow and I think this patch will improve things a lot already.

[yrodiere]

I included this in #35407, so if that one gets merged we'll want to close this one.

[gsmet]

Let's keep them separate as I like keeping track of my work in PRs.

[quarkus-bot]

Failing Jobs - Building fce2443

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✔️	JVM Tests - JDK 17
✖	JVM Tests - JDK 17 Windows	Build	Failures	Logs	Raw logs
✖	JVM Tests - JDK 20	Build	⚠️ Check →	Logs	Raw logs

Full information is available in the Build summary check run.

Failures

⚙️ JVM Tests - JDK 17 Windows #

- Failing: extensions/grpc/deployment 
! Skipped: extensions/micrometer-registry-prometheus/deployment extensions/micrometer/deployment extensions/opentelemetry/deployment and 52 more

📦 extensions/grpc/deployment

✖ io.quarkus.grpc.server.MutinyGrpcServiceWithSSLTest.testEmptyWithMutinyClient - More details - Source on GitHub

io.smallrye.mutiny.TimeoutException
	at io.smallrye.mutiny.operators.uni.UniBlockingAwait.await(UniBlockingAwait.java:64)
	at io.smallrye.mutiny.groups.UniAwait.atMost(UniAwait.java:65)