Support functional setFunctionBreakpoints command

[st0012]

Currently, DAP server responds to setFunctionBreakpoints command but it doesn't really do anything. This PR enables adding/removing method breakpoints.

Supported breakpoint types:

class Foo
  def foo
  end

  def self.bar
  end
end

foo = Foo.new

• Foo#foo - will stop at Foo's instance method foo
• Foo.bar - will stop at Foo's singleton method bar

This is not intentionally supported but currently it works:

• foo.foo - will stop at foo object's #foo method call

Condition is also supported:

Demos

Function Breakpoint

Function.breakpoints.mov

Function Breakpoint with Conditions

Function.breakpoints.with.condition.mov

[peterzhu2118]

bp["condition"] here could be the empty string if the user first creates a condition, then deletes the condition. We should treat an empty string like nil (i.e. no condition) instead of like a false condition, so we should turn the empty string into nil.

[peterzhu2118]

Is this method used anywhere?

[peterzhu2118]

This test doesn't really test when condition evaluates to true.

[peterzhu2118]

This breakpoint wouldn't have triggered anyways since it doesn't match anything in the code.