Improve scalability of HttpCookieStore.Default

[sbordet]

Jetty version(s)
12.0.x

Description
HttpCookieStore.Default uses a lock to protect the data structures holding the cookies.

However, it is rare that cookies are added, and much more common that cookies are read, so it should be a good case to use ReentrantReadWriteLock.

[joakime]

Another change you can add, for performance reasons, is the limits outlined in RFC6265: Section 5.3 - Storage Model.

   At any time, the user agent MAY "remove excess cookies" from the
   cookie store if the number of cookies sharing a domain field exceeds
   some implementation-defined upper bound (such as 50 cookies).

   At any time, the user agent MAY "remove excess cookies" from the
   cookie store if the cookie store exceeds some predetermined upper
   bound (such as 3000 cookies).

50 cookies max per shared domain.
3000 cookies max per cookie store.

Configurable, of course.