Address reviewer feedback on the Maven toolchains dedup logic:
- Treat jdk toolchains without a string `provides.id` as non-deduplicatable
and use optional access when comparing ids, so partially-formed or
nonstandard toolchains.xml files no longer crash setup.
- Preserve the existing `<toolchains>` root attributes (xmlns,
schemaLocation, …) when present, falling back to the 1.1.0 defaults only
for attributes the existing file is missing. This avoids silently
rewriting user-managed metadata or changing the effective namespace.
Adds tests covering custom root attributes and id-less jdk toolchains, and
rebuilds dist/.
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
On self-hosted runners toolchains.xml may survive multiple runs and unexpectedly
grow as a result of the toolchains setup simply appending the JDK definition
even if one with the same `type` and `provides.id` already exists.
Restructuring the parsing step and filtering the potentially existing list of
toolchain definitions prevents this and also fixes toolchain.xml files that
already contain duplicates.
Fixes#530
