Merge #154: qt: Support macOS Dark mode

dc4551c remove incompatibility release note for darkmode on macos (Sylvain Goumy)
303cfc6 allow darkmode on macos build (Sylvain Goumy)
78f75a2 Allow icon colorization on mac os to better support dark mode (Uplab)

Pull request description:

  Allow icons to be colorized on macOS to support native Dark mode color scheme.

  Rendering on macOS Big Sur before PR:
  ![macos-darkmode-before-pr](https://user-images.githubusercontent.com/5577626/102502739-43f3af80-407f-11eb-9263-5bbc27b371c2.png)

  Rendering on macOS Big Sur after PR:
  ![macos-darkmode-after-pr](https://user-images.githubusercontent.com/5577626/102502678-350cfd00-407f-11eb-8b98-e271f2688c36.png)

  Light mode stay visually unchanged.

  <del>Note, that this currently only affect the build from source, as the macos dmg includes an attributes to force light color scheme on macos windows (see bitcoin/bitcoin#14593). </del>
  <del>But once all glitches are fixed, we will be able to remove this temporary fix. </del>
  Edit: this PR is know including the removal of `NSRequiresAquaSystemAppearance` on Info.plist file so that the color fix is apply to every build.

  Linked issues: #68 #136

ACKs for top commit:
  hebasto:
    re-ACK dc4551c
  jarolrod:
    ACK dc4551c

Tree-SHA512: 1c3a4dec796063e61fcaf80112afc2b15c8669a1cd30ebd537cea96647c20215f8f80289719f905820bb0c490c8c1f94bfae4bb32f9c6d1fdd4e8f199ebb559f

doc/release-notes.md

@@ -51,9 +51,7 @@ Core should also work on most other Unix-like systems but is not as
 frequently tested on them.  It is not recommended to use Bitcoin Core on
 unsupported systems.
 
-From Bitcoin Core 0.22.0 onwards, macOS versions earlier than 10.14 are no
-longer supported. Additionally, Bitcoin Core does not yet change appearance
-when macOS "dark mode" is activated.
+From Bitcoin Core 22.0 onwards, macOS versions earlier than 10.14 are no longer supported.
 
 Notable changes
 ===============

share/qt/Info.plist.in

@@ -60,9 +60,6 @@
   <key>NSHighResolutionCapable</key>
     <string>True</string>
 
-  <key>NSRequiresAquaSystemAppearance</key>
-    <string>True</string>
-
   <key>LSApplicationCategoryType</key>
     <string>public.app-category.finance</string>
 </dict>

src/qt/platformstyle.cpp

@@ -18,7 +18,7 @@ static const struct {
     /** Extra padding/spacing in transactionview */
     const bool useExtraSpacing;
 } platform_styles[] = {
-    {"macosx", false, false, true},
+    {"macosx", false, true, true},
     {"windows", true, false, false},
     /* Other: linux, unix, ... */
     {"other", true, true, false}