chore: remove dead build scripts containing supply-chain vulnerability

Remove the entire .buildscript/ directory and release.sh — all dead code
from a legacy CircleCI/Bintray era with zero references from active CI.

e2e.sh downloaded and executed a remote script from the unowned rudderio
GitHub org via wget|bash, which exfiltrates system info to an attacker
endpoint. release.sh sent credentials to the defunct Bintray API whose
domain could be re-registered. deploy_snapshot.sh hardcoded rudderio as
the authorised deployer. The remaining files (cli.sh, bootstrap.sh,
settings.xml) were orphaned.

Also removes the commented-out settings.xml reference from pom.xml.

🔒 Scanned for secrets using gitleaks 8.28.0

Author: 1abhishekpandey

.buildscript/bootstrap.sh

@@ -337,7 +337,6 @@
                     <!--<autoVersionSubmodules>true</autoVersionSubmodules>
                     <checkModificationExcludes>
                         <checkModificationExclude>pom.xml</checkModificationExclude>
-                        <checkModificationExclude>.buildscript/settings.xml</checkModificationExclude>
                     </checkModificationExcludes>
                     <autoReleaseAfterClose>true</autoReleaseAfterClose>-->
                 </configuration>