Intern timeout error strings

[kriskowal]

A production heap snapshot revealed that 47% of an aberrant process’s memory was consumed by strings, mostly timeout exception strings (long paths redacted):

TchannelRequestTimeoutError: request timed out after 101ms (limit was 100ms)
 at Object.createError [as RequestTimeoutError] (hyperbahn/node_modules/tchannel/node_modules/error/typed.js:31:22)
 at LazyRelayOutReq.onTimeout hyperbahn/node_modules/tchannel/relay_handler.js:601:27)
 at TimeHeap.callExpiredTimeouts (hyperbahn/node_modules/tchannel/time_heap.js:186:14)
 at TimeHeap.drainExpired (hyperbahn/node_modules/tchannel/time_heap.js:175:14)
 at TimeHeap.update (hyperbahn/node_modules/tchannel/time_heap.js:116:10)
 at Operations.addInReq (hyperbahn/node_modules/tchannel/operations.js

Let’s reduce the weight of these strings by removing the stack trace and memoizing/interning strings for combinations snapped to 10ms.