A significant amount of time is spent generating the string
representation for the proc.Registers object of each thread, since this
field is rarely used (only when the Registers API is called) it should
be generated on demand.
Also by changing the internal representation of proc.Register to be
closer to that of op.DwarfRegister it will help us implement #1838
(when Delve will need to be able to display the registers of an
internal frame, which we currently represent using op.DwarfRegister
objects).
Benchmark before:
BenchmarkConditionalBreakpoints-4 1 22292554301 ns/op
Benchmark after:
BenchmarkConditionalBreakpoints-4 1 17326345671 ns/op
Reduces conditional breakpoint latency from 2.2ms to 1.7ms.
Updates #1549, #1838
