tests: internal: uri: add test code

[nokute78]

This patch is to

• Add test code for flb_uri
• Prevent passing negative pos

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Enter [N/A] in the box, if an item is not applicable to your change.

Testing
Before we can approve your change; please submit the following in a comment:

• [N/A] Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

Debug/Valgrind output

d$ valgrind --leak-check=full bin/flb-it-uri 
==28059== Memcheck, a memory error detector
==28059== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==28059== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==28059== Command: bin/flb-it-uri
==28059== 
Test uri_create_destroy...                      [ OK ]
==28060== Warning: invalid file descriptor -1 in syscall close()
==28060== 
==28060== HEAP SUMMARY:
==28060==     in use at exit: 0 bytes in 0 blocks
==28060==   total heap usage: 850 allocs, 850 frees, 87,507 bytes allocated
==28060== 
==28060== All heap blocks were freed -- no leaks are possible
==28060== 
==28060== For lists of detected and suppressed errors, rerun with: -s
==28060== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Test uri_get...                                 [ OK ]
==28061== Warning: invalid file descriptor -1 in syscall close()
==28061== 
==28061== HEAP SUMMARY:
==28061==     in use at exit: 0 bytes in 0 blocks
==28061==   total heap usage: 850 allocs, 850 frees, 87,507 bytes allocated
==28061== 
==28061== All heap blocks were freed -- no leaks are possible
==28061== 
==28061== For lists of detected and suppressed errors, rerun with: -s
==28061== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Test uri_encode...                              [ OK ]
==28062== Warning: invalid file descriptor -1 in syscall close()
==28062== 
==28062== HEAP SUMMARY:
==28062==     in use at exit: 0 bytes in 0 blocks
==28062==   total heap usage: 847 allocs, 847 frees, 87,340 bytes allocated
==28062== 
==28062== All heap blocks were freed -- no leaks are possible
==28062== 
==28062== For lists of detected and suppressed errors, rerun with: -s
==28062== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
SUCCESS: All unit tests have passed.
==28059== 
==28059== HEAP SUMMARY:
==28059==     in use at exit: 0 bytes in 0 blocks
==28059==   total heap usage: 3 allocs, 3 frees, 1,109 bytes allocated
==28059== 
==28059== All heap blocks were freed -- no leaks are possible
==28059== 
==28059== For lists of detected and suppressed errors, rerun with: -s
==28059== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

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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.