feat: add xmllint for XML validation, fix flint.toml exclude format

Adds cargo:xmloxide which installs the xmllint binary — validates
well-formedness of all *.xml files (pom.xml, version-rules.xml, etc.).

Also migrates flint.toml from the old exclude/exclude_paths fields to
the new single glob list format (required by current flint v2).

Signed-off-by: Gregor Zeitlinger <gregor.zeitlinger@grafana.com>

Author: zeitlinger

.github/config/flint.toml

@@ -1,9 +1,9 @@
 [settings]
-exclude = "src/main/generated"
-exclude_paths = [
-    "docs/themes/",
+exclude = [
+    "src/main/generated/**",
+    "docs/themes/**",
     "mvnw",
-    "simpleclient-archive/",
+    "simpleclient-archive/**",
 ]
 
 [checks.renovate-deps]

.github/renovate-tracked-deps.json

@@ -165,6 +165,7 @@
     "mise": [
       "actionlint",
       "cargo:https://github.com/grafana/flint",
+      "cargo:xmloxide",
       "editorconfig-checker",
       "github:google/google-java-format",
       "go:github.com/gohugoio/hugo",

mise.toml

@@ -2,6 +2,7 @@
 "cargo:https://github.com/grafana/flint" = "branch:feat/flint-v2"
 "go:github.com/gohugoio/hugo" = "v0.157.0"
 "go:github.com/grafana/oats" = "0.6.1"
+"cargo:xmloxide" = "0.4.1"
 "github:google/google-java-format" = "1.26.0"
 actionlint = "1.7.10"
 editorconfig-checker = "v3.6.1"