Add optional retry for transient CensusGeocoder failures

[JakeSelby]

What is this change?

• censusgeocode re-raises RequestException and CensusGeocoder never caught it, so a single
  connection reset or timeout ended the whole call. For geocode_address_batch that means a long
  job dies partway through its chunks.
• Adds a retries constructor argument and a _request helper that retries connection-level
  failures with 2 ** attempt backoff. The retry wraps the per-chunk call in
  geocode_address_batch, so completed chunks are never re-sent.
• Fixes [Feature/Addition] Optional retry for transient CensusGeocoder request failures #1931.

Considerations for discussion

• The default is 0, which preserves today's behavior exactly. Retrying by default would
  change request timing for every existing user and could multiply load on a government endpoint,
  so it seemed wrong to opt everyone in. Newmode defaults to 2 retries if you would rather this
  matched that.
• Only RequestException is retried, and that is a real limit worth naming. censusgeocode
  never calls raise_for_status(), so the Census API's own error responses do not raise: a 5xx
  reaches _fetch as a JSON decode failure and surfaces as
  ValueError("Unable to parse response from Census"), which is indistinguishable from a genuine
  parse problem. Retrying ValueError would therefore also retry real bugs, so I left it alone.
  Making HTTP status failures visible is a separate change and I have filed it separately.
• Put on the constructor rather than each method, matching Redshift, Postgres, MySQL and
  Braintree.

How to test the changes (if needed)

uv run --no-default-groups --group test --extra geocode pytest test/test_geocode

Four new tests cover recovery after transient failures, re-raising once retries are exhausted,
the no-retry default, and that all four public methods are wrapped.

Breaking Changes

Breaking changes are changes to our public API which may require existing users to change their code. If there are no breaking changes, any existing parsons user should not need to do anything after updating their parsons version.

Does this PR introduce breaking changes?

• label: Breaking change — This PR introduces one or more breaking changes.
• label: Non-breaking change — This PR does not introduce one or more breaking changes.

Details (if needed)

• New optional keyword argument defaulting to 0, which makes exactly one attempt and never
  sleeps -- identical to current behavior. No signature or return-type change.

[bmos]

Suggested change

	def _request(self, func, *args, **kwargs):
	# Retries transient network failures only; see the class docstring for the limits.
	def _request(self, func, *args, **kwargs):
	"""
	Facilitate retrying requests when network failures occur.
	Failed requests resulting in retries will be logged.
	See class docstring for more information.
	Args:
	func (Callable): function to wrap with retry logic
	Returns:
	Value returned by provided callable
	"""

Doesn't have to be exactly that, but a docstring here would be nice.