[REM] fields: remove fields.Any, temporary artifact for ill-typed fields

This was added in master-apiculture at f1f16a8 to
permit special function fields that return
structured JSON-like data.
This is unnecessary and caused typing problems, for
example for the type field of ir.model.fields, or
when you decide to store them.

It is simpler to explicitly declare these fields
as fields.Char and have them serialize their results
to JSON strings, or to declate them as fields.Binary
and return any opaque data they want.
[FIX] google_calendar: cleanup/spellcheck translatable terms
[IMP] tools.translate: unused import
[IMP] BaseModel: new `_translate` attribute to disable translations

Can be defined to False in any model to completely
disable translations for this model, when they are
irrelevant. This is useful e.g. for test classes
that use attributes that would normally be translatable.
[IMP] website: disable translation exports for test models

Avoids noise in POT files
[FIX] website.menu: url field should not be translated

Pages are made translatable using a dedicated mechanism,
and there is no UI to translate menu URLs anyway.
[FIX] snippets: avoid orphan full stop (.)
[ADD] safe_eval: allow YIELD_VALUE, used e.g. for generator comprehension
[IMP] website: update sample social media accounts
[IMP] website: unused imports
[IMP] website: disable translations for example URLs
[FIX] models: fixes #1017; do not update list in place in the construction of _depends on models