fix: keep network search field enabled after clearing calls (#9855)

* fix: keep network search field enabled after clearing calls

The Network screen search field was gated on whether any requests were present, so clearing all calls left the field disabled and the query could no longer be edited. Drop the hasRequests gate so the field stays enabled at all times, matching the default search field behavior used elsewhere in DevTools.

Fixes #9853

* Add release note entry for network search field fix (#9855)

* refactor: drop redundant filteredData listener in network controls

The network search field is now always enabled and no longer reads
controller.filteredData in build, so this listener only forced needless
rebuilds of the controls row on every filter change.

* fix: reload network test fixtures each test to prevent shared-ref drain

Clear button mutations on httpProfile/socketProfile in FakeVmServiceWrapper
clear the underlying lists in place. Since setUpAll shared the same fixture
refs across all tests, a test that taps Clear would leave empty profiles for
the next test. Move fixture load to setUp so each test gets fresh instances.

Fixes CI failures on test_ddc and test_dart2js.

* fix: restore IdeTheme global in network profiler test setUpAll

* test: restore httpProfile load in setUpAll

Keep loading both fixtures in setUpAll like before; the per-test reload in the group setUp is what guarantees a clean copy for the clear-calls test.