This commit adds a new attribute mode for position 'replace' to the xpath feature.
This mode can take 2 values:
- 'outer' (default mode if not provided) that will replace the sibling target
- 'inner' that will preserve the sibling target
If base arch is:
```html
<p>
<field name='x'>yyy</field>
</p>
```
`<field name='x' position="replace" (mode="outer")>zzz</field>`
```html
<p>
zzz
</p>
```
`<field name='x' position="replace" mode="inner">zzz</field>`
```html
<p>
<field name='x'>
zzz
</field>
</p>
```
Mode inner is useful for theme or render flat content, but not recommanded to
be used in page editable since we ignore the inherit-branding part until now.
task-2172208
closesodoo/odoo#48679
Signed-off-by: Jérémy Kersten (jke) <jke@openerp.com>
Co-authored-by: Okan SUMER (osu) <osu@odoo.com>
Co-authored-by: Jérémy Kersten <jke@odoo.com>
