Make endpoint-rules blob internal and add C2J skip flag

[sbiscigl]

Description of changes:

Steps toward migrating endpoint resolution from the JSON ruleset to BDD bytecode. The JSON blob and its GetRulesBlob/RulesBlobSize accessors are an internal detail of the JSON representation we're replacing never meant to be public.

• New --skip-endpoint-rules-blob flag (default off). When set, C2J omits the JSON blob body + GetRulesBlob() from EndpointRules.*. Threaded like the existing --skip-model-generation. Default-off = no change for services that don't opt in.
• Stop exporting the blob symbols (always on). They were leaking into the dynamic symbol table on GCC/Clang via default visibility.

Check all that applies:

• Did a review by yourself.
• Added proper tests to cover this PR. (Codegen-template change; verified by generated-output inspection — flag off = blob emitted as before, flag on = absent. Existing EndpointProviderTests still exercise the provider.)
• Checked if this PR is a breaking (APIs have been changed) change. Yes — see below.
• Checked if this PR will not introduce cross-platform inconsistent behavior. (Reduces it: Linux/macOS now match Windows, which never exported these.)
• Checked if this PR would require a ReadMe/Wiki update.

Breaking note: Removes GetRulesBlob/RulesBlobSize/RulesBlobStrLen from the exported ABI on Linux/macOS (accidentally exported; Windows never did). Normal client users unaffected. Only code that directly instantiates EndpointProvider must recompile.

Check which platforms you have built SDK on to verify the correctness of this PR.

• Linux
• Windows
• Android
• MacOS
• IOS
• Other Platforms

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