Description of the issue/feature this PR addresses:

Installing Odoo via the .deb package continuously causes issues with the asset bundles. This is because of the following daisy chain of behaviors:

- `dpkg-buildpackage` parses `SOURCE_DATE_EPOCH` from debian/changelog and then clamps the Modified date of all files to at max that epoch ([src](https://launchpad.net/debian/+source/dpkg/1.18.8)). The relevate date is the one written after the email in the topmost changelog entry
- This is preserved when unpacking the .deb package, the OS does not change it
- The Asset loading logic in ir.qweb and ir.asset relies on the Modified date (via [`os.path.getmtime`](https://github.com/odoo/odoo/blob/17.0/odoo/addons/base/models/ir_asset.py#L49)) to determine the hash that serves a Version for the asset bundles ([src](https://github.com/odoo/odoo/blob/17.0/odoo/addons/base/models/assetsbundle.py#L775), [src](https://github.com/odoo/odoo/blob/17.0/odoo/addons/base/models/assetsbundle.py#L148))
- The controller and ir.qweb compiler rely on this Version hash to correctly invalidate outdated asset bundles and force re-generation of the bundle content as neccessary

Current behavior before PR:

debian/changelog has not been changed or maintained since 2020 and its timestamp remains `Tue, 15 Dec 2020 10:28:49 +0100` This results in the Modified Date being clamped to 2020, which means the files no matter how much is changed always look like last modified on this date. Therefore the Version hash for the asset bundles never changes, and the asset reload logic does not trigger correctly.
This is especially dangerous for setups which use several code sources with different file delivery methods, for example installing Community via .deb but Enterprise via git. This results in only some asset bundles not being updated (those not touched by Enterprise modules) while others are, which then generates an OWL error as it detects the content being different between the bundles ([src](https://github.com/odoo/odoo/blob/17.0/addons/web/static/lib/owl/owl.js#L3333))
For versions 18+, a very common result of this behavior is the portal chatter failing to work. This is because the same files like for example mail/static/src/core/common/thread.xml being loaded into both [`portal.assets_chatter`](https://github.com/odoo/odoo/blob/18.0/addons/portal/__manifest__.py#L69), which is not touched by an Enterprise module, but also into [`web.assets_frontend`
](https://github.com/odoo/odoo/blob/18.0/addons/im_livechat/__manifest__.py#L90) via im_livechat, which is a bundle touched by many modules, including Enterprise modules. Thus, is a file in the mail addon is changed, the changes are correctly applied to `web.assets_frontend`, but not `portal.assets_chatter`, causing an OWL error. This is extremely frustrating to fix, since it not only requires a manual Asset Rebuild, but also for every user to empty their Browser Cache, since the assets bundles are so large as to be guaranteed to be cached, and if the old version of the bundle is loaded from cache, the OWL error persists. A similar error can also happen with website, since the assets for the WYSIWIG editor are loaded as a module-specific bundle, `website.assets_wysiwyg`, which also fails to update, while of course the same assets being loaded to the general website asset bundle will be updated.

Desired behavior after PR is merged:

The builder for the nightly .deb package of Odoo writes a complete debian/changelog entry instead of merely replacing the first line. This entry includes the current date, thus ensuring the Modified date for the files is not clamped to years in the past. Down the line, this fixes the assets loading issue.


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