Replace usages of AssertLegacyTrait::assert(No)FieldById, that is deprecated

Problem/Motivation

AssertLegacyTrait::assertFieldById() is deprecated in drupal:8.2.0 and is removed from drupal:10.0.0. Use $this->assertSession()->fieldExists() or $this->assertSession()->buttonExists() or $this->assertSession()->fieldValueEquals() instead. See https://www.drupal.org/node/3129738

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet