DRIVERS-3011 test relaxed encoding of dates after year 9999

[kevinAlbs]

Summary

Test encoding dates after year 9999 with Relaxed Extended JSON

Background & Motivation

The extended JSON spec notes:

BSON 1.1 Type or Convention	Canonical Extended JSON Format	Relaxed Extended JSON Format
...
Datetime [year before 1970 or after 9999]	{"$date": {"$numberLong": <64-bit signed integer giving millisecs relative to the epoch, as a string>}}	<Same as Canonical Extended JSON>

This tests reveals a bug in the C driver encoding: CDRIVER-5759.

As a drive-by fix, missing \ escapes were added to < characters in the Conversion table:

Before:

After:

Please complete the following before merging:

- [ ] Update changelog.
- [ ] Make sure there are generated JSON files from the YAML test files.

• Test changes in at least one language driver. Verified by C driver tests with fix
  - [ ] Test these changes against all server versions and topologies (including standalone, replica set, sharded
  clusters, and serverless).