Support the retrieval of standard names for EC parameters

Internally, the JDK supports well-known names that identify the precomputed parameters associated with standardised elliptic curves. Currently there is no public API to retrieve that list which makes the java.security.spec.ECGenParameterSpec class awkward to use when generating the specification for an
elliptic curve.

Introduce a public API to retrieve the list of the standard names available for generating the (precomputed) elliptic curve domain parameters.

In addition, to promote wider EC adoption, the standardised Brainpool elliptic curves (RFC 5639)
should also be included in the list of standard names available via ECGenParameterSpec.


Note that the ability to generate the necessary parameters for a particular elliptic curve is no guarantee that
the curve is supported in any specific JCE provider. For example, the SunEC provider supports the
SEC2/NIST and ANSI X9.62 curves but not the Brainpool curves.