[Bug] Build info semver parsing fails on -SNAPSHOTs

[andrewazores]

          I'm getting an error upon agent startup after this change:

Exception in thread "cryostat-agent-main" Exception in thread "cryostat-agent-main" java.lang.NumberFormatException: For input string: "0-SNAPSHOT"
	at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
	at java.base/java.lang.Integer.parseInt(Integer.java:668)
	at java.base/java.lang.Integer.parseInt(Integer.java:786)
	at io.cryostat.agent.VersionInfo$Semver.fromString(VersionInfo.java:109)
	at io.cryostat.agent.VersionInfo.load(VersionInfo.java:50)
	at io.cryostat.agent.Agent.accept(Agent.java:210)
	at io.cryostat.agent.Agent.lambda$agentmain$0(Agent.java:160)
	at java.base/java.lang.Thread.run(Thread.java:840)
java.lang.NumberFormatException: For input string: "0-SNAPSHOT"
	at java.base/java.lang.NumberFormatException.forInputString(NumberFormatException.java:67)
	at java.base/java.lang.Integer.parseInt(Integer.java:668)
	at java.base/java.lang.Integer.parseInt(Integer.java:786)
	at io.cryostat.agent.VersionInfo$Semver.fromString(VersionInfo.java:109)
	at io.cryostat.agent.VersionInfo.load(VersionInfo.java:50)
	at io.cryostat.agent.Agent.accept(Agent.java:210)
	at io.cryostat.agent.Agent.lambda$agentmain$0(Agent.java:160)
	at java.base/java.lang.Thread.run(Thread.java:840)

Originally posted by @ebaron in #508 (comment)