Add TLS compatibility mode configuration for HTTP senders

[adhamahmad]

Summary

Adds support for configuring TLS compatibility mode for HTTP senders (OkHttp only for now), allowing clients to optionally connect to endpoints that require legacy TLS protocol versions.

Fixes #7573

Motivation

Some users running on legacy environments, may be unable to connect to endpoints that only support older TLS protocol versions. The current HTTP sender configuration only supports modern TLS negotiation, preventing connections to these legacy endpoints.

Changes

Added TlsCompatibilityMode configuration to HttpSenderConfig with MODERN as the default behavior
Added HttpExporterBuilder.setTlsCompatibilityMode(TlsCompatibilityMode) to allow OTLP HTTP exporters to configure TLS compatibility behavior
Updated ImmutableHttpSenderConfig to carry the TLS compatibility mode configuration
Updated OkHttpHttpSender to map TlsCompatibilityMode.COMPATIBLE to OkHttp's ConnectionSpec.COMPATIBLE_TLS
Kept existing behavior unchanged by defaulting all senders to modern TLS configuration
Added TlsCompatibilityMode as a public API for implementation-neutral TLS compatibility configuration
Updated public API diff documentation with the new configuration method and enum

Testing

Added OkHttpHttpSenderTlsCompatibilityTest
Verified MODERN mode cannot connect to a server restricted to TLSv1/TLSv1.1 protocols
Verified COMPATIBLE mode can negotiate a connection with a legacy TLS-only server

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: adhamahmad / name: Adham Ahmed Hussein Mahrous (6473f3a)

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-sdk-common

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[jack-berg]

Hey I gave this issue some thought and shared my analysis here: #7573 (comment)

I think we should go in a different direction with this: #8610, which embodies option d in the comment.

[opentelemetry-pr-dashboard]

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