RFR: 8342808: Javadoc should add whitespace between type parameters

[Nizar Benalla]

Please review this patch to render javadocs as `<K, V, T>` rather than `<K,V,T>` to match naming conventions and make the rendered output slighly nicer to read.

Passes langtool tests.

The generated docs only includes `java.base/lang`, `java.base/util` and `java.compiler/javax`

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Commit messages:
 - Add small whitespace before map parameters

Changes: https://git.openjdk.org/jdk/pull/21759/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21759&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342808
  Stats: 64 lines in 9 files changed: 0 ins; 1 del; 63 mod
  Patch: https://git.openjdk.org/jdk/pull/21759.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21759/head:pull/21759

PR: https://git.openjdk.org/jdk/pull/21759