Add methods to get name of SendableChooser's selected value

[Braykoff]

In some cases, such as logging, it can be useful to get the name of a SendableChooser's currently selected option. This adds:

• getSelectedName()/GetSelectedName(), to get the name of the currently selected option
• onChange(BiConsumer<String, V>)/OnChange(std::function<void(std::string_view, T)> listener) to get the name when the currently selected option changes. The original onChange methods are kept for backward compatibility.

[Braykoff]

/format

[Gold856]

/format was removed. You'll have to format manually.

[KangarooKoala]

Great work! I'm really hopeful that this can make it in before kickoff. Just a few things:

• You can change the first 7 lines of GetSelected() (currently 98-104) to just std::string selected = GetSelectedName(); to match Java.
• Java's testChangeListener() doesn't have the changes done to C++'s ChangeListener test.

[Braykoff]

It seems an unrelated test has failed in ubsan:

[----------] Global test environment tear-down
[==========] 401 tests from 68 test suites ran. (7832 ms total)
[  PASSED  ] 400 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] DifferentialDrivetrainSimTest.Convergence

 1 FAILED TEST

[PeterJohnson]

Suggested change

	std::string_view GetSelectedName() const {
	std::string GetSelectedName() const {

It's not safe to return a string_view here. It needs to return a copy (a std::string) because the access is mutex-protected, so (theoretically) another thread could come in and modify m_selected before the string_view is accessed.

[PeterJohnson]

Suggested change

	std::string_view selected = GetSelectedName();
	std::string selected = GetSelectedName();