(PE-3914) Addressed PR feedback and bumped up a couple of dependencies.

This commit does the following:

* Bumps up the `certificate-authority` and `http-client` dependencies to
  a later version.

* Changed `crl-path` references to `ssl-crl-path`.

* Flattened `WebserverSslCrlPath` schema define into `schema/maybe schema/Str`
  references.

* Changed `ssl-context-factory` to accept a map of
  `WebserverSslContextFactory`, a new schema type, instead of discrete
  keystore, client-auth, and ssl-crl-path options.