[codegen] Fix getImportMap stripping extensions from 3rd party library names

[art-alexeyenko]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

When codebase includes imports from 3rd party libraries with names like jazz.js, the .js part would be stripped when building import map.
This PR fixes it.

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[github-actions]

📦 Package Size and Test Coverage Report

Package	Base Size	PR Size	Δ Change	Base Coverage	PR Coverage	Δ Change
analytics-core	122.52 KB	122.52 KB	✅ 0.00 KB	100.00%	100.00%	0.00%
cli	58.70 KB	58.70 KB	✅ 0.00 KB	69.73%	69.73%	0.00%
content	399.19 KB	397.70 KB	🔻 -1.49 KB	92.18%	92.26%	+0.07%
core	95.15 KB	95.15 KB	✅ 0.00 KB	92.12%	92.12%	0.00%
create-content-sdk-app	243.64 KB	243.64 KB	✅ 0.00 KB	96.22%	96.22%	0.00%
events	76.91 KB	76.91 KB	✅ 0.00 KB	98.40%	98.40%	0.00%
nextjs	430.44 KB	430.44 KB	✅ 0.00 KB	89.73%	89.73%	0.00%
personalize	63.45 KB	63.45 KB	✅ 0.00 KB	99.32%	99.32%	0.00%
react	289.47 KB	289.47 KB	✅ 0.00 KB	93.63%	93.63%	0.00%
search	7.11 KB	7.11 KB	✅ 0.00 KB	98.57%	98.57%	0.00%
Total	—	—	🔻 -1.49 KB	—	—	—