tests: Add fuzzing harness for strprintf(…)

[practicalswift]

Add fuzzing harness for strprintf(…).

Update FuzzedDataProvider.h.

Avoid hitting some issues in tinyformat (reported upstreams in c42f/tinyformat#70).

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Found issues in tinyformat:

Issue 1. The following causes a signed integer overflow followed by an allocation of 9 GB of RAM (or an OOM in memory constrained environments):

strprintf("%.777777700000000$", 1.0);

Issue 2. The following causes a stack overflow:

strprintf("%987654321000000:", 1);

Issue 3. The following causes a stack overflow:

strprintf("%1$*1$*", -11111111);

Issue 4. The following causes a NULL pointer dereference:

strprintf("%.1s", (char *)nullptr);

Issue 5. The following causes a float cast overflow:

strprintf("%c", -1000.0);

Issue 6. The following causes a float cast overflow followed by an invalid integer negation:

strprintf("%*", std::numeric_limits<double>::lowest());

[maflcko]

When updating FuzzedDataProvider, please include the exact commit id that it was updated to

[practicalswift]

@MarcoFalke Good point! Done! :)

[maflcko]

ACK

nit: in the commit that bumps the provider: Could limit the commit subject to a reasonable length, i.e. move the url to the commit body

[practicalswift]

@MarcoFalke Thanks for reviewing! Feedback addressed. Please re-review :)

[chamajcpradel]

Sirs. This is very good test.

[Empact]

Would be helpful to comment on "why" in each commit message - e.g. I was curious to look into why the FuzzedDataProvider.h update was necessary and found that the ConsumeFloatingPoint was introduced recently. https://chris.beams.io/posts/git-commit/#why-not-how