Feat: Added Utility to fetch the branch using the branch alias and added it to export plugin and version bump

[cs-raj]

• Add utility to fetch the branch using the branch alias
• Using the utility before the branch setup in export
• Flags introduced in export plugin --branch-alias and short -b for adding the alias during the command execution
• The flag is exclusive of branch flag

version bump:
"@contentstack/cli-audit": "~1.14.1",
"@contentstack/cli-auth": "~1.6.1",
"@contentstack/cli-cm-bootstrap": "~1.15.1",
"@contentstack/cli-cm-branches": "~1.5.1",
"@contentstack/cli-cm-bulk-publish": "~1.9.1",
"@contentstack/cli-cm-clone": "~1.15.2",
"@contentstack/cli-cm-export": "~1.20.0",
"@contentstack/cli-cm-export-to-csv": "~1.9.1",
"@contentstack/cli-cm-import": "~1.26.3",
"@contentstack/cli-cm-import-setup": "1.4.2",
"@contentstack/cli-cm-migrate-rte": "~1.6.1",
"@contentstack/cli-cm-seed": "~1.12.1",
"@contentstack/cli-command": "~1.6.1",
"@contentstack/cli-config": "~1.15.1",
"@contentstack/cli-migration": "~1.8.1",
"@contentstack/cli-utilities": "~1.14.0",
"@contentstack/cli-variants": "~1.3.1",