zstd: introduce zstd compression support in Fluent Bit (cleanup)

[edsiper]

The following PR introduces ZSTD compression support in Fluent Bit:

• adds zstd v1.56 (bundled library)
• new flb_zstd.c compress/uncompress interface
• internal interface unit tests
• opentelemetry output: add support for compress: zstd
• opentelemetry input: add support to detect and uncompress zstd

Test: Fluent Bit --> OpenTelemetry Collector

bin/fluent-bit -i dummy -p dummy="{\"zstd\": \"ok\"}" -o opentelemetry -p port=4318 -p compress=zstd

opentelemetry-collector:

2025-01-13T18:53:30.506-0600	info	Logs	{"kind": "exporter", "data_type": "logs", "name": "debug", "resource logs": 1, "log records": 1}
2025-01-13T18:53:30.506-0600	info	ResourceLog #0
Resource SchemaURL: 
ScopeLogs #0
ScopeLogs SchemaURL: 
InstrumentationScope  
LogRecord #0
ObservedTimestamp: 1970-01-01 00:00:00 +0000 UTC
Timestamp: 2025-01-14 00:53:29.832229967 +0000 UTC
SeverityText: 
SeverityNumber: Unspecified(0)
Body: Map({"zstd":"ok"})
Trace ID: 
Span ID: 
Flags: 0
	{"kind": "exporter", "data_type": "logs", "name": "debug"}

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.