Add mvn targets for GraalVM Enterprise PGO

[edbratt]

Consider adding build targets for GraalVM Enterprise PGO

This can be accomplished using cmd arguments:
mvn package -DbuildArgs="--pgo-instrument" -Pnative-image
for generating the profile generation build. Followed by
mvn clean package -DbuildArgs="--pgo=./default.iprof" -Pnative-image
For example, maybe add targets like:
-Pnative-image-pgo-instrument
-Pnative-image-pgo

Might also consider updating the .gitignore to avoid inadvertent check-in of the resulting iprof files.