refactor: simplify Reporter interface

[LukeWinikates]

This refactor simplifies the Reporter interface by pushing a conditional from the caller into the Report method and eliminating ReportEvent from the interface.

• simplifies code at the call site
• makes the interface smaller
• applies Tell, Don't Ask

[jbooherl]

LGTM

[LukeWinikates]

• verify that the behavior change for the event sender doesn't pose any problems
  - [ ] Wavefront API should be able to handle sending gzipped events
  - [ ] Wavefront proxy should be able to handle gzipped event lines

[LukeWinikates]

Just wrote some additional tests, sending an event directly to Wavefront and sending an event via my local Wavefront proxy.

Neither approach actually supports gzip - the proxy rejects it like this:

Proxy response to gzipped payload

2023-10-26 13:39:35,171 INFO  [AbstractReportableEntityHandler:reject] [2878] blocked input: [WF-300 Cannot parse metric: "�rp-K�+Q04��065�47543��LL!<������<�T�R%����[��|���BIb��Rqrj^bQf��BJfQjr�ny�nI~vj� ��8�Cb source="localhost""; remote: 0:0:0:0:0:0:0:1 [2878]; reason: "Invalid value: ��8�Cb"]

WF API response to gzipped JSON

{"status":{"result":"ERROR","message":"Illegal character ((CTRL-CHAR, code 31)): only regular white space (\\r, \\n, \\t) is allowed between tokens\n at [Source: (org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$UnCloseableInputStream); line: 1, column: 2]","code":400}}

Without gzip, both work fine - so I will remove the gzip code path for events in this PR.

[LukeWinikates]

@jbooherl @suprajanarasimhan made a couple more changes here. Still basically the same change, but I removed the line that sets the gzip header, and I added a bunch of tests. I'll probably merge this tomorrow.