Allow re-initialize of tokenizer

[acatav]

Problem

Global tokenizer not allow re-initialize. This make it harder to work with notebooks the often re-run cells, and also to change the tokenizer as you go

Solution

Allow re-initialization of tokenizer

Type of Change

• 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 not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

Changed according test

[igiloh-pinecone]

LGTM.

See one test suggestion