Set both DEVELOCITY_ACCESS_KEY and GRADLE_ENTERPRISE_ACCESS_KEY env vars (#225)

Follow up of https://github.com/gradle/actions/pull/224, we now attempt to set both old and new access key env variables to a short lived token.
If a short-lived token cannot be obtained, then:
- DEVELOCITY_ACCESS_KEY is set to an empty string, preventing this from being used.
- GRADLE_ENTERPRISE_ACCESS_KEY is left intact, with a deprecation warning being issued.

sources/src/configuration.ts

@@ -188,6 +188,9 @@ export enum JobSummaryOption {
 }
 
 export class BuildScanConfig {
+    static DevelocityAccessKeyEnvVar = 'DEVELOCITY_ACCESS_KEY'
+    static GradleEnterpriseAccessKeyEnvVar = 'GRADLE_ENTERPRISE_ACCESS_KEY'
+
     getBuildScanPublishEnabled(): boolean {
         return getBooleanInput('build-scan-publish') && this.verifyTermsOfUseAgreement()
     }
@@ -201,7 +204,12 @@ export class BuildScanConfig {
     }
 
     getDevelocityAccessKey(): string {
-        return core.getInput('develocity-access-key') || process.env['DEVELOCITY_ACCESS_KEY'] || ''
+        return (
+            core.getInput('develocity-access-key') ||
+            process.env[BuildScanConfig.DevelocityAccessKeyEnvVar] ||
+            process.env[BuildScanConfig.GradleEnterpriseAccessKeyEnvVar] ||
+            ''
+        )
     }
 
     getDevelocityTokenExpiry(): string {