fix(chat): fix tokenizer issue (Issue #2753)

[Gimir]

Description:

• add js-tiktoken package (deduplication made)
• replace getEncoding method which was using wasm with browser supported method from js-tiktoken

Issues:

• Issue [Tech Debt] inverstigate the issues with sudden reloading Dial chat application (often in development mode) #2753

Checklist:

• the pull request name complies with Conventional Commits
• the pull request name starts with fix(<scope>):, feat(<scope>):, feature(<scope>):, chore(<scope>):, hotfix(<scope>): or e2e(<scope>):. If contains breaking changes then the pull request name must start with fix(<scope>)!:, feat(<scope>)!:, feature(<scope>)!:, chore(<scope>)!:, hotfix(<scope>)!: or e2e(<scope>)!: where <scope> is name of affected project: chat, chat-e2e, overlay, shared, sandbox-overlay, etc.
• the pull request name ends with (Issue #<TICKET_ID>) (comma-separated list of issues)
• I confirm that do not share any confidential information like API keys or any other secrets and private URLs

[Gimir]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-2763.nightly-test.deltixhub.io
E2E tests status: success

[IlyaBondar]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-2763.nightly-test.deltixhub.io
E2E tests status: failed

[Gimir]

/deploy-review

Environment URL: https://chat-ai-dial-chat-pr-2763.nightly-test.deltixhub.io
E2E tests status: success