[ADD] [web_export_view] export all records if all checkbox is selected

[hbrunn]

this allows to export all records when the all records checkbox is selected.

I wasn't very happy with the implementation choice of fishing out the data from the DOM, that's why I changed this to read from the underlying dataset. Commit 5ca37d4 contains a version that manipulates the DOM to do what we want, but that's slow and very unwieldy. What do @eLBati @simahawk @StefanRijnhart @lepistone (current contributors) think?

[lepistone]

Hi @hbrunn ! I haven't been involved with this for a while now. I'll let the others speak out. Thanks!

[StefanRijnhart]

Thanks! I tested this change succesfully exporting both individual records and all records. I also checked the correct formatting of floats with different decimal separators.

[eLBati]

Thanks.
Should the same be applied to the more recent versions of odoo?

[hbrunn]

if we agree this is a cleaner implementation and if I didn't destroy any feature this way, yes, I think we should (being unsure if this tacitly removes some feature is the reason I harassed all contributors I could find)

[StefanRijnhart]

I'd merge, but it needs a version bump

[hbrunn]

right, thanks. Any reasons for not having a CI check for this? (it's my understanding that actually applying the rules means a version bump for a changed comma)