This adds a fast path to skip runtime calls to GetSubstitution when
the replacer string does not contain a '$' char.

Extended background:

String.prototype.replace is (roughly) structured as follows:

* Check if {searchValue} has a @@replace Symbol, and delegate to that if
  so. We currently implement efficient fast paths when {searchValue} is
  a String or a fast RegExp.
* A specialized fast path for single-char {searchValue}, "long" subject
  string, and String {replaceValue} that do not contain '$' chars (yes,
  this fast path is very specialized).
* Check for the location of the first match using StringIndexOf, and
  exit early if no match is found.
* Finally build the return value, which is 'prefix + replacement +
  suffix', where replacement is either the result of calling {replaceValue}
  (if it is callable), or GetSubstitution(ToString({replaceValue}))
  otherwise.

There's several spots that could be improved.

StringIndexOf currently calls into C++ runtime for all but the simple
1-byte, 1-char {searchValue} case. We need to finally add support for
remaining cases.

The runtime call to GetSubstitution can be skipped if the replacer
string does not contain any '$' syntax. This CL handles that case.

BUG=

Review-Url: https://codereview.chromium.org/2813843002
Cr-Commit-Position: refs/heads/master@{#44606}