Refactor OSD element display code

Remove the giant `select` block that contained all the code to generate the elements and transition them to individual functions called only when the element is active. Simplifies the code and results in a performance improvement as it's not necessary to fall through the large `select` statement for every element that will be drawn. The individual functions and the element to function mapping are moved to a new `osd_elements.c` file.

Moved the OSD related code files to a new `osd/` directory.

Also pre-analyze the active elements and only process those that are active. This also saves processing as it's not necessary to loop through all 50 or so elements when only a couple are active.

Various other cleanup and removal of stale or unnecessary code.

In the default configuration the element drawing phase of the OSD task is reduced from ~51us to ~35us - resulting in about a 30% decrease in processing time.

src/test/unit/cli_unittest.cc

@@ -40,11 +40,11 @@ extern "C" {
     #include "flight/servos.h"
     #include "io/beeper.h"
     #include "io/ledstrip.h"
-    #include "io/osd.h"
     #include "io/serial.h"
     #include "io/vtx.h"
     #include "msp/msp.h"
     #include "msp/msp_box.h"
+    #include "osd/osd.h"
     #include "pg/pg.h"
     #include "pg/pg_ids.h"
     #include "pg/beeper.h"

src/test/unit/osd_unittest.cc

@@ -52,7 +52,9 @@ extern "C" {
 
     #include "io/beeper.h"
     #include "io/gps.h"
-    #include "io/osd.h"
+
+    #include "osd/osd.h"
+    #include "osd/osd_elements.h"
 
     #include "sensors/acceleration.h"
     #include "sensors/battery.h"
@@ -62,7 +64,6 @@ extern "C" {
 
     void osdRefresh(timeUs_t currentTimeUs);
     void osdFormatTime(char * buff, osd_timer_precision_e precision, timeUs_t time);
-    void osdFormatTimer(char *buff, bool showSymbol, int timerIndex);
     int osdConvertTemperatureToSelectedUnit(int tempInDegreesCelcius);
 
     uint16_t rssi;
@@ -481,6 +482,8 @@ TEST(OsdTest, TestAlarms)
     osdConfigMutable()->cap_alarm  = 2200;
     osdConfigMutable()->alt_alarm  = 100; // meters
 
+    osdAnalyzeActiveElements();
+
     // and
     // this timer 1 configuration
     osdConfigMutable()->timers[OSD_TIMER_1] = OSD_TIMER(OSD_TIMER_SRC_ON, OSD_TIMER_PREC_HUNDREDTHS, 2);
@@ -562,6 +565,8 @@ TEST(OsdTest, TestElementRssi)
     osdConfigMutable()->item_pos[OSD_RSSI_VALUE] = OSD_POS(8, 1) | OSD_PROFILE_1_FLAG;
     osdConfigMutable()->rssi_alarm = 0;
 
+    osdAnalyzeActiveElements();
+
     // when
     rssi = 1024;
     displayClearScreen(&testDisplayPort);
@@ -595,6 +600,8 @@ TEST(OsdTest, TestElementAmperage)
     // given
     osdConfigMutable()->item_pos[OSD_CURRENT_DRAW] = OSD_POS(1, 12) | OSD_PROFILE_1_FLAG;
 
+    osdAnalyzeActiveElements();
+
     // when
     simulationBatteryAmperage = 0;
     displayClearScreen(&testDisplayPort);
@@ -628,6 +635,8 @@ TEST(OsdTest, TestElementMahDrawn)
     // given
     osdConfigMutable()->item_pos[OSD_MAH_DRAWN] = OSD_POS(1, 11) | OSD_PROFILE_1_FLAG;
 
+    osdAnalyzeActiveElements();
+
     // when
     simulationMahDrawn = 0;
     displayClearScreen(&testDisplayPort);
@@ -677,6 +686,8 @@ TEST(OsdTest, TestElementPower)
     // given
     osdConfigMutable()->item_pos[OSD_POWER] = OSD_POS(1, 10)  | OSD_PROFILE_1_FLAG;
 
+    osdAnalyzeActiveElements();
+
     // and
     simulationBatteryVoltage = 1000; // 10V
 
@@ -739,6 +750,8 @@ TEST(OsdTest, TestElementAltitude)
     // given
     osdConfigMutable()->item_pos[OSD_ALTITUDE] = OSD_POS(23, 7) | OSD_PROFILE_1_FLAG;
 
+    osdAnalyzeActiveElements();
+
     // and
     osdConfigMutable()->units = OSD_UNIT_METRIC;
     sensorsClear(SENSOR_GPS);
@@ -800,6 +813,8 @@ TEST(OsdTest, TestElementCoreTemperature)
     // given
     osdConfigMutable()->item_pos[OSD_CORE_TEMPERATURE] = OSD_POS(1, 8) | OSD_PROFILE_1_FLAG;
 
+    osdAnalyzeActiveElements();
+
     // and
     osdConfigMutable()->units = OSD_UNIT_METRIC;
 
@@ -846,6 +861,8 @@ TEST(OsdTest, TestElementWarningsBattery)
     osdWarnSetState(OSD_WARNING_BATTERY_CRITICAL, true);
     osdWarnSetState(OSD_WARNING_BATTERY_NOT_FULL, true);
 
+    osdAnalyzeActiveElements();
+
     // and
     batteryConfigMutable()->vbatfullcellvoltage = 410;
 

src/test/unit/rcdevice_unittest.cc

@@ -40,9 +40,10 @@ extern "C" {
 
     #include "scheduler/scheduler.h"
     #include "io/rcdevice_cam.h"
-    #include "io/osd.h"
     #include "io/rcdevice.h"
 
+    #include "osd/osd.h"
+
     #include "pg/pg.h"
     #include "pg/pg_ids.h"
     #include "pg/vcd.h"