When plugins change their 'parameter info' this often means that their
previous parameter text is no longer valid, so we should fetch new text
to represent the parameter value.

This change was primarily tested with Kontakt.

Note that hosts using the AUv2 API (e.g. JUCE hosts) to host JUCE AUv3
plugins may not receive begin/end gesture events, depending on the OS
version, and potentially the host architecture. I suspect this is
because older versions of the OS-provided AUv2/AUv3 translation layer
don't handle these events.

In testing, an Intel host on Catalina did not receive begin/end events,
but an Arm host on Monterey did receive these events.

This change was tested with FabFilter Pro Q 3, which supports new AU
channel layouts for Atmos.

This issue affected windows with JUCE titlebars. When dragging the
window back and forth between two displays with different DPI settings,
the window could sometimes end up with the wrong size.

It looks like setting new window bounds inside the WM_WINDOWPOSCHANGED
message was occasionally causing the system to lose track of the correct
scale for the window.

As a byproduct of this change, JUCE should no longer receive reentrant
calls to handleDPIChanging.

With this patch applied, the DemoRunner should build under MinGW, and be
(nearly) feature-complete compared to the MSVC build.

Specifically, when building with MinGW:
- Adds support for accessibility
- Fixes build issues in the juce_video module
- Fixes a link issue in the VST3 wrapper when VST3_CAN_REPLACE_VST2 is
  defined
- Adds support for the new-style native FileChooser
- Tidies up some other low-severity warnings

Known issues:
- Direct2D rendering is still not supported when building with MinGW due
  to ABI compatibilities.

Previously, with two instances of the MIDILogger AUv3 in series in
Logic, the timestamps received by the second plugin in the chain would
not match the timestamps of the events emitted by the first plugin.