test: Misc logs fixes

[kaylareopelle]

Fixes a few things from previously merged logs content:

• test: Add LogRecordProcessor tests
• test: Update observed_timestamp LogRecord test (Tests for timestamp were updated to use Time objects, but
  observed_timestamp was not. Now, they both evaluate Time. They are turned into floats when converted to LogRecordData.)
  test: Exclude test directory from SimpleCov (this leads to more accurate coverage percentages)
  style: Misc docs/spacing updates

[mwear]

I'm still noticing occasional flakes similar to:

  1) Error:
OpenTelemetry::SDK::Logs::Export::BatchLogRecordProcessor::#on_emit#test_0003_logs a warning if a log record was emitted after the buffer is full:
MockExpectationError: expected warn("1 log record(s) dropped. Reason: buffer-full") => nil
    org/jruby/RubyHash.java:1615:in `each'
    test/opentelemetry/sdk/logs/export/batch_log_record_processor_test.rb:220:in `block in <main>'
    org/jruby/RubyArray.java:1981:in `each'
    org/jruby/RubyArray.java:2803:in `map'

Here's an example: https://github.com/open-telemetry/opentelemetry-ruby/actions/runs/10605899311/job/29434936693?pr=1697

Were any of these fixes expected to address this?

[kaylareopelle]

I'm still noticing occasional flakes similar to ... Were any of these fixes expected to address this?

@mwear - These fixes weren't intended to address the flakes. I'm planning to take care of those with #1701 and will work on that later this week.

[kaylareopelle]

@mwear - Until I can put in a real fix, I think we should skip this test for JRuby. Does that sound good to you?