Retry artifacts after 2h, not 24h, for melt/smelt

This uses a newly added feature of pombast to specify a settings.xml
file to use with relevant pombast actions like melt and smelt
(see scijava/pombast@12a42f6).
In such a file, we can set the updatePolicy of each repository.

It is tempting to pass -U to all of pombast's mvn invocations, forcing
rechecks for missing artifacts every single time. But that would be
overkill, adding more overhead to each smelt component build, whereas
reducing the update window from 24 hours to 2 hours means that we
won't recheck for (probably still) missing artifacts for every smelted
component that depends on it during a single run, but rather we'll
recheck "soon" -- hopefully the next time CI runs ~2 hours later.

Why 2 hours? Because the pombast CI smelt run takes ~90 minutes when
no previous successes have been cached. Would it be better to somehow
reset the last-checked metadata before starting the smelt, so that
every CI build behaves as though it's the first one of the day?
Perhaps! But for now, let's try the 2h interval and see how it goes.

Author: ctrueden

pombast.toml

@@ -1,6 +1,7 @@
 [common]
 default-java-version = 8
 repositories = ["scijava.public=https://maven.scijava.org/content/groups/public"]
+settings = "pombast/settings.xml"
 
 [status]
 output = "target/pombast/index.html"

pombast/settings.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<settings>
+  <profiles>
+    <profile>
+      <id>update-interval</id>
+      <repositories>
+        <repository>
+          <id>scijava.public</id>
+          <url>https://maven.scijava.org/content/groups/public</url>
+          <releases><updatePolicy>interval:120</updatePolicy></releases>
+          <snapshots><updatePolicy>interval:120</updatePolicy></snapshots>
+        </repository>
+        <repository>
+          <id>central</id>
+          <url>https://repo.maven.apache.org/maven2</url>
+          <releases><updatePolicy>interval:120</updatePolicy></releases>
+        </repository>
+      </repositories>
+    </profile>
+  </profiles>
+  <activeProfiles><activeProfile>update-interval</activeProfile></activeProfiles>
+</settings>