Add formatter

[lavaleri]

Issue #, if available:

Description of changes:

• Add https://github.com/coveooss/fmt-maven-plugin to pom
• Add Codebuild to specifically check the format
• Run autoformatter tool in order to pass this new check

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Check any applicable:

• Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.

[lavaleri]

Confirmed no bytecode difference between this branch and master using jardiff

[lavaleri]

To check byte code difference:

• checkout this branch, mvn clean, mvn install
• mv ./target/aws-encryption-sdk-java-2.3.0.jar ./after.jar
• checkout master branch, mvn clean mvn install
• mv ./target/aws-encryption-sdk-java-2.3.0.jar ./before.jar
• install jardiff: https://github.com/scala/jardiff
• jardiff before.jar after.jar
• confirm that any output is just pom or META-INF updates

To verify doc changes:

• checkout this branch, mvn clean, mvn javadoc:javadoc
• mv target/site afterdocs
• checkout master branch, mvn clean, mvn javadoc:javadoc
• mv target/site beforedocs
• strip newlines and <!--Generatedbyjavadoc(11.0.10)onWedMayXXXX:XX:XXPDT2021--> tags from both afterdocs and beforedocs using your favorite regex!
• diff -r beforedocs afterdocs
• confirm there is no output