Implement BufferedByteLimit option

[cisetn]

Summary

Added support for BufferedByteLimit in Google Pub/Sub messages.

Changes

1. Added the BufferedByteLimit option to the Fluent Bit configuration to allow controlling the buffer size limit.
2. Updated the README to include the BufferedByteLimit option.

Testing

All new and existing tests have been run to ensure that the changes are functioning as expected.

output:

=== RUN   TestEncodeToJSON
=== RUN   TestEncodeToJSON/simple_map
=== RUN   TestEncodeToJSON/nested_map
=== RUN   TestEncodeToJSON/invalid_key_type
=== RUN   TestEncodeToJSON/nested_slice
=== RUN   TestEncodeToJSON/byte_value
=== RUN   TestEncodeToJSON/nested_byte_slice
=== RUN   TestEncodeToJSON/nested_interface
=== RUN   TestEncodeToJSON/deeply_nested_slice
--- PASS: TestEncodeToJSON (0.00s)
    --- PASS: TestEncodeToJSON/simple_map (0.00s)
    --- PASS: TestEncodeToJSON/nested_map (0.00s)
    --- PASS: TestEncodeToJSON/invalid_key_type (0.00s)
    --- PASS: TestEncodeToJSON/nested_slice (0.00s)
    --- PASS: TestEncodeToJSON/byte_value (0.00s)
    --- PASS: TestEncodeToJSON/nested_byte_slice (0.00s)
    --- PASS: TestEncodeToJSON/nested_interface (0.00s)
    --- PASS: TestEncodeToJSON/deeply_nested_slice (0.00s)
=== RUN   TestFLBPluginInit
--- PASS: TestFLBPluginInit (0.01s)
=== RUN   TestFLBPluginFlush
--- PASS: TestFLBPluginFlush (5.49s)
=== RUN   TestInterfaceToBytes
--- PASS: TestInterfaceToBytes (0.00s)
=== RUN   TestNewKeeper
--- PASS: TestNewKeeper (0.03s)
=== RUN   TestGooglePubSub_Send
--- PASS: TestGooglePubSub_Send (5.27s)
=== RUN   TestGooglePubSub_Stop
--- PASS: TestGooglePubSub_Stop (0.02s)
PASS
coverage: 73.2% of statements
ok  	github.com/st-tech/fluent-bit-pubsub-custom	12.194s	coverage: 73.2% of statements

Additional Information

None