[FIX] web_editor: indent just a line inside table
[FIX] web_editor: indent just a line inside table

Inside the cell of a table, indenting had several behaviors:

- if the selection is contained in several nodes elements: indent the
  element child nodes of common ancestor

- if the selection is contained in one or more list items: indent these
  list items

- if the selection is contained in one 'content block': indent the whole
  cell content

The two first behaviors are expected, but the third one is a little odd
and unexpected next to other existing editors behaviors.

With this commit, the third behavior becomes:

- if the selection is contained in one `content block`: indent this
  content block

note: 'content block' is defined as p, pre, h1, h2, ..., blockquote, td

opw-1824647
closes #24182

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo