v0.152.0

New tag {% attrs %}, more powerful alternative to {% html_attrs %}

The new {% attrs %} tag accepts dicts, optionally lists or nested lists of dicts.
```
{% attrs some_dict {"data-extra": 123} %}
```
Merging: Old {% html_attrs %} merged all attributes. {% attrs %} merges only class and style. For other attributes, the last one wins. This is now aligned with Vue's behavior.

class and style still accept strings, dicts, and lists:
```
{% attrs {
    "class": ["rounded", {"shadow": True}],
    "style": ["color: red;", {"color": "blue"}],
} %}
```
Rendered directly, the result is an escaped, space-delimited HTML attribute string:
```
<div {% attrs {"id": "1"} {"data-extra": 123} %}></div>
          ↓
<div id="1" data-extra="123"></div>
```
When {% attrs %} is the only tag in component's input, the component receives the dictionary without serialization:
```
{% component "table"
    table_attrs="{% attrs [base_attrs, {'class': 'compact'}] %}"
/ %}
```
Use the compose_attrs() helper in Python.

The existing {% html_attrs %} tag and merge_attributes() helper keep their old behavior.

format_attributes() and the new attrs tag now reject invalid runtime HTML attribute names.

See #1703.