feat: Add opportunistic Brotli compression (#3612)

Brotli level 4 and 5 offer comparable or better compression to GZip
level 9 (which is our default) with better performance. This patch
adds opportunistic Brotli compression at level 4 (to be conservative)
when it detects the `brotli` module is available. It also provides some
escape hatches through `transport_compression_level` and
`transport_compression_algo` experiment configs to fine tune the behavior.

In the future, we may want to bump the default level from 4 to 5 for better
compression.

---------

Co-authored-by: Ivana Kellyer <[email protected]>

Author: BYK

Diff for: requirements-testing.txt

@@ -13,3 +13,4 @@ pysocks
 socksio
 httpcore[http2]
 setuptools
+Brotli

Diff for: sentry_sdk/consts.py

@@ -18,6 +18,11 @@ class EndpointType(Enum):
     ENVELOPE = "envelope"
 
 
+class CompressionAlgo(Enum):
+    GZIP = "gzip"
+    BROTLI = "br"
+
+
 if TYPE_CHECKING:
     import sentry_sdk
 
@@ -59,6 +64,8 @@ class EndpointType(Enum):
             "continuous_profiling_mode": Optional[ContinuousProfilerMode],
             "otel_powered_performance": Optional[bool],
             "transport_zlib_compression_level": Optional[int],
+            "transport_compression_level": Optional[int],
+            "transport_compression_algo": Optional[CompressionAlgo],
             "transport_num_pools": Optional[int],
             "transport_http2": Optional[bool],
             "enable_metrics": Optional[bool],