fix(components): enable any async EIP to reuse main MDC context

[squakez]

• Added a stack based MDC push/pop, by storing temporary the context before the exchange execution and setting back after it.
• We cannot reliably clean the context at the end of the async execution as other processes (eg, InterceptSendToEndpoint EIP) could need to use the context previously set. In any case, this is not a consistency break, as, by design, we always reset the MDC context before any execution (either sync or async).
• The only side effect is that the unit tests cannot check any longer that there is no MDC context as, this will be maintained (as required by those EIP mentioned earlier).

Closes CAMEL-22717

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[squakez]

@Croway thanks for the review comment, now the tests are much more idiomatic, please, have a look.

[squakez]

To cherrypick the other PRs doc and unit test developed.