feat: q to bool

[VladislavYar]

Description

Added __bool__ support to the Q class, allowing Q objects to be evaluated in a boolean context.

A Q object is considered truthy if it contains any filters or any non-empty children. An empty Q() with no filters and no children evaluates to False.

Motivation and Context

Previously, all Q instances were truthy by default (standard Python object behavior), making it impossible to distinguish between an empty Q() and a meaningful one. This change enables natural boolean checks like if q: to guard against applying empty query conditions.

How Has This Been Tested?

Added test_q_to_bool covering four cases:

Q(row="data") - truthy (has filters)
Q() - falsy (no filters, no children)
Q(Q(row="data"), Q(row="data")) - truthy (has non-empty children)
Q(Q(), Q()) - falsy (all children are empty)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks

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_{Comparing VladislavYar:q-to-bool (67f957a) with develop (bc4f971)}

[waketzheng]

Please add more test cases, such as:

q = ~q
q = Q(Q(), Q(), join_type='OR')
...

[waketzheng]

How about using the following code?

if self.filters:
    return True
return any(self.children)

[waketzheng]

It would be better to also update the changelog.