Java Driver: fix pre-existing broken links found by local linkcheck run

[nikagra]

While working on #204, a local make -C docs linkcheck run on the java-driver source revealed 18 additional pre-existing broken links beyond those covered by that issue.

These are not regressions — they were present before and are unrelated to the changes in scylladb/java-driver#926.

---

Broken links by category

Old Javadoc anchor format (pre-Java 9 #method-Param.Type- → post-Java 9 #method(Param.Type))

File	Broken anchor
manual/core/custom_codecs/README.md	java/util/Optional.html#empty--
manual/core/custom_codecs/README.md	java/lang/Enum.html#name--
manual/core/custom_codecs/README.md	java/lang/Enum.html#ordinal--
manual/core/performance/README.md	CqlSession.html#prepare-com.datastax.oss.driver.api.core.cql.SimpleStatement-
manual/core/reactive/README.md	ReactiveResultSet.html#getColumnDefinitions--
manual/core/reactive/README.md	ReactiveResultSet.html#getExecutionInfos--
manual/core/reactive/README.md	ReactiveResultSet.html#wasApplied--
manual/core/statements/README.md	Session.html#execute-com.datastax.oss.driver.api.core.cql.Statement-
manual/core/statements/README.md	Session.html#executeAsync-com.datastax.oss.driver.api.core.cql.Statement-
manual/mapper/daos/insert/README.md	ResultSet.html#getExecutionInfo--

Third-party docs restructured / anchors renamed

File	Broken URL	Notes
manual/core/configuration/README.md	github.com/typesafehub/config#standard-behavior	Repo renamed to lightbend/config; anchor gone
manual/core/graalvm/README.md	graalvm.org/.../BuildConfiguration/#embedding-a-configuration-file	GraalVM docs restructured
manual/core/statements/prepared/README.md	github.com/google/guava/wiki/CachesExplained#reference-based-eviction	Guava wiki anchor renamed
manual/developer/netty_pipeline/README.md	netty.io/wiki/requirements-for-4.x.html#tls-with-openssl	Netty wiki restructured
manual/developer/netty_pipeline/README.md	netty.io/4.1/api/.../SslContextBuilder.html#forClient--	Old Javadoc anchor format
manual/developer/netty_pipeline/README.md	netty.io/4.1/api/.../SslContext.html#newHandler-io.netty.buffer.ByteBufAllocator-	Old Javadoc anchor format
manual/mapper/config/kotlin/README.md	kotlinlang.org/docs/reference/kapt.html#using-in-gradle	Kotlin docs restructured
manual/mapper/config/kotlin/README.md	kotlinlang.org/docs/reference/kapt.html#using-in-maven	Kotlin docs restructured
manual/mapper/config/kotlin/README.md	kotlinlang.org/docs/reference/using-maven.html#compiling-kotlin-and-java-sources	Kotlin docs restructured
manual/core/reactive/README.md	reactive-streams/reactive-streams-jvm#2.2	GitHub anchor encoding
manual/query_builder/idempotence/README.md	wikipedia.org/.../Linearizability#Definition_of_linearizability	Wikipedia anchor renamed
upgrade_guide/README.md	DataStax FAQ #where-is-downgrading-consistency-retry-policy	Dead page

Bot-blocked / dead download URLs (likely false positives or genuinely dead)

File	URL	Notes
manual/core/compression/README.md	java-performance.info/performance-general-compression/	403
manual/core/compression/README.md	search.maven.org/search?q=g:com.datastax.oss...	403 bot-block
manual/core/integration/README.md	search.maven.org/#search%7Cga%7C1%7C...	Old Maven search URL
manual/core/integration/README.md	search.maven.org/search?q=g:com.datastax.oss	403 bot-block
manual/core/integration/README.md	downloads.datastax.com/java-driver/	Dead download page
index.md	search.maven.org/#search%7Cga%7C1%7Cg%3A%22com.scylladb%22	Old Maven search URL