[FIX] website_event_booth_sale: display price correction

Steps to reproduce:
- Create a price list with different currency and discount with "show price and discount to the customer"
- On the website select this pricelist and try to select the booth

Issue:
The displayed price will not be the correct one

Note:
This is an issue discovered during the correction of https://github.com/odoo/odoo/pull/101375 (forward-port of https://github.com/odoo/odoo/pull/85640

)
It allows to have the correct price depending of the currency of the pricelist applied.
Now the unlink of the rate makes the new rate directlt effective. There is no need of having a `new_company` anymore.

Summary:
- view modification in `website_event_booth_sale` -> price of selected booth,  simplification of comparison for the `<del>`
- view modification in `website_event_sale` : simplification of comparison for the `<del>`
- backend test modification in `website_event_[booth_]sale` common: addapt the rate; take out useless `new_env`; simplified pricelists creation
- tour test addition:  added the tour for essential use cases in event and event_booth; simplified the command so it is more readable

related ticket:
opw-2766997

closes odoo/odoo#101559

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>