[16.0][FIX] base_tier_validation: Field merge in view

[houzefa-abba]

Previous implementation was losing fields in some cases; new one properly merges dicts/tuples.

This fixes odd "Missing field string information" errors in form-embedded lists.

This cset also removes an obsolete base_model_name context key no longer used in Odoo 16.

This cset adds a test_get_view test which checks for that need_validation field; it was failing with the previous impl.

Fixes #825.