build: upgrade to java 17 and update CI workflows

[antriksh-9]

Changes Made:

• upgraded project to java 17
• upgraded springboot version to 2.7.18 (java 17 compatible)
• updated spotless for java 17 compatibility
• modernise gradle plugin configuration [removed buildscript]
• updated CI workflows to use java 17
• added JAXB dependencies (required for java 17)

Validation:

• local build succeeds with ./gradle clean build
• code works with both java -jar as well as docker container

Fixes:

• Upgrade Gradle, Java version in code and CI and SpringBoot #494

[preetkaran20]

Thanks for the PR.Some small failures, I am merging this and then will update it with another PR.
@antriksh-9 thanks for the changes.