[Doc] Add explanation on how to use take_object_by_id in tests

[lxfind]

Add tutorial in the second chapter to explain how to take objects using ID when there are multiple of the same type.
Also rename get_last_created_object_id to last_created_object_id to make it shorter.

[Clay-Mysten]

Thanks, Xun! Markdown LGTM.

[codecov]

Codecov Report

Merging #1584 (60ce918) into main (c1e46f0) will decrease coverage by 3.75%.
The diff coverage is 64.94%.

@@            Coverage Diff             @@
##             main    #1584      +/-   ##
==========================================
- Coverage   82.19%   78.43%   -3.76%     
==========================================
  Files         104      122      +18     
  Lines       21145    21895     +750     
==========================================
- Hits        17380    17174     -206     
- Misses       3765     4721     +956     

Impacted Files	Coverage Δ
faucet/src/errors.rs	0.00% <0.00%> (ø)
faucet/src/requests.rs	0.00% <0.00%> (ø)
faucet/src/responses.rs	0.00% <0.00%> (ø)
network_utils/src/network.rs	36.64% <0.00%> (-0.78%)	⬇️
sui/src/benchmark.rs	0.00% <0.00%> (ø)
sui/src/benchmark/bench_types.rs	0.00% <0.00%> (ø)
sui/src/benchmark/load_generator.rs	0.00% <0.00%> (ø)
sui/src/benchmark/transaction_creator.rs	0.00% <0.00%> (ø)
sui/src/benchmark/validator_preparer.rs	0.00% <0.00%> (ø)
sui/src/bin/sui-move.rs	3.12% <ø> (ø)
... and 115 more

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