[hal, wpilib] Add OpMode support (#7744)

User code:
- OpModeRobot used as the robot base class
- LinearOpMode and PeriodicOpMode are provided opmode base classes
- In Java, annotations can be used to automatically register opmode classes

Additional user code functionality:
- OpMode (string) is available in addition to the overall
auto/teleop/test robot mode
- OpMode does not indicate enable (enable/disable is still separate)
- The HAL API uses integer UIDs; these are exposed at the user API level
as well for faster checks
- User code creates opmodes on startup (these have name, category,
description, etc).

DS:
- DS will present opmode selection lists for auto and teleop for
match/practice. During a match, the DS will automatically activate the
selected opmode in the corresponding match period.
- For testing, an overall mode is selected (e.g. teleop/auto/test) and a
single opmode is selected

Future work:
- Command framework support/integration
- Python annotation support
- Unit tests (needs race-free DS sim updates)
- Porting of examples

Co-authored-by: Joseph Eng <91924258+KangarooKoala@users.noreply.github.com>

docs/build.gradle

@@ -164,6 +164,7 @@ task generateJavaDocs(type: Javadoc) {
             "-org.wpilib.hardware.hal," +
             "-org.wpilib.hardware.hal.simulation," +
             // TODO: ^ Document these, then remove them from the list
+            "-org.wpilib.hardware.hal.struct," +
             "-org.wpilib.math.proto," +
             "-org.wpilib.math.struct," +
             "-org.wpilib.math.controller.proto," +