Add option to disable normalize embeddings after calculating emphasis

[hako-mikan]

Description

In SDXL, there have been reports of artifacts occurring when combining prompts or using long prompts. I have discovered the cause of this phenomenon. It is the normalization that occurs after the calculation of emphasis. During this normalization, artifacts arise due to division by values close to zero and the inversion of signs. This normalization process dates back to the SD1.X era, where it seems to work well. However, in certain models of XL, it appears to have the opposite effect. Therefore, I will add an option to toggle this normalization on and off.
The detailed explanation can be found here or here(Japanese)

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests

[catboxanon]

Since this PR was also made upstream, it should (ideally) get merged there, and then it'll be synced to this repo, assuming I understood what was described in #80. PR #60 was closed for a similar reason.

This seems like something important to address in general for future PRs that modify modules that came from upstream, but that decision probably falls on @lllyasviel.

[lllyasviel]

yes prs related to webui should go upstream