RUBY-3424 Prep for 2.20

[jamis]

Preparing for the 2.20 release. I probably did not need to deprecate 2.7 and JRuby 9.2, and add JRuby 9.4, in this release, but I did it anyway. :) The effort involved was minimal.

N.B.: The two failing specs are known and will be addressed in RUBY-3423 (related to rangePreview on latest server).

Proposed release announcement:

Ruby Driver 2.20.0 Released

Version 2.20.0 of the Ruby driver for MongoDB is released. This adds the following new features:

• Connection strings no longer require a slash between the hosts and the options. E.g., "mongodb://example.com?w=1" and "mongodb://example.com/?w=1" are both valid connection strings now. (https://jira.mongodb.org/browse/RUBY-3329)
• Container runtime and orchestration metadata for the client environment are now sent to the server for analytics purposes. (https://jira.mongodb.org/browse/RUBY-3298)
• When connecting to a CosmosDB (Azure) or DocumentDB (Amazon) instance, a warning message will now be logged. (https://jira.mongodb.org/browse/RUBY-3296)
• When attempting a retry of a read or write operation in a sharded topology, the retry will be attempted on a different mongos instance, if possible. (https://jira.mongodb.org/browse/RUBY-2748)
• Add support for the newly-released Ruby-BSON version 5.0.
• Support for Ruby 2.5 and 2.6 has been discontinued. Support for Ruby 2.7 and JRuby 9.2 has been deprecated, and will be discontinued in a future driver version. Support for JRuby 9.4 has been added.

This release also fixes the following user-facing issues:

• The driver will now raise an error if start_transaction is invoked and the server deployment does not support transactions. (https://jira.mongodb.org/browse/RUBY-1791)
• Encountering a network error when a session is live will mark the session dirty and discard it, preventing the session from being reused when it is likely to fail. (https://jira.mongodb.org/browse/RUBY-1813)
• Tailable cursors would terminate early, after reading existing documents, instead of waiting for more. (https://jira.mongodb.org/browse/RUBY-3332)
• There was an issue where writes could fail with an exception if no session was active. (https://jira.mongodb.org/browse/RUBY-3358)