[Client] Added an exclude and color identity filter for the visual database display (#7587)

* [Client] Add exclude and color identity filters to the visual database display

* [Filters] Extract the color filter mode derivation into libcockatrice_filters

The mode table and the 'which mode produced this filter set' derivation are
filter semantics, not widget code, so they belong next to CardFilter rather
than in an anonymous namespace in the client. Moving them also makes them
testable: filter_mode_test pins every mode, the Custom fallback and the
'keep the live mode when it still fits' rule.

* [Tests] Cover the negated color identity query

ci! read the camelCase colorIdentity property instead of the lowercase
coloridentity key, so it matched the empty string and rejected every card.
The new case uses a card whose colors and color identity differ, so it fails
on the old lookup and passes on the fixed one.

---------

Co-authored-by: Lukas Brübach <44814898+BruebachL@users.noreply.github.com>

libcockatrice_card/libcockatrice/card/card_info.cpp

@@ -316,6 +316,10 @@ void CardInfo::setColors(const QString &value)
 {
     setProperty(Mtg::Colors, value);
 }
+QString CardInfo::getColorIdentity() const
+{
+    return getProperty(Mtg::ColorIdentity);
+}
 QString CardInfo::getLoyalty() const
 {
     return getProperty(Mtg::Loyalty);

libcockatrice_card/libcockatrice/card/card_info.h

@@ -469,6 +469,7 @@ public:
     [[nodiscard]] QString getCmc() const;
     [[nodiscard]] QString getColors() const;
     void setColors(const QString &value);
+    [[nodiscard]] QString getColorIdentity() const;
     [[nodiscard]] QString getLoyalty() const;
     [[nodiscard]] QString getMainCardType() const;
     [[nodiscard]] QString getManaCost() const;