Make TCTI configurable and force the tests to use the simulator

[diabonas]

This PR makes allows configuring the TCTI to be used with

• an additional TSS2_TCTI_CONTEXT argument (can be NULL) for the library functions and
• the new -T/--tcti option or the environment variable TPM2TOTP_TCTI for the tpm2-totp command.

The syntax and the implementation for the command option/environment variable follow the implementations in tpm2-tools (https://github.com/tpm2-software/tpm2-tools/pull/765, tpm2_options.c and tpm2_tcti_ldr.c) and tpm2-tss-engine (https://github.com/tpm2-software/tpm2-tss-engine/pull/62, tpm2-tss-engine-tcti.c).

Using these configuration options, we can force the tests to use the TPM simulator, enabling the possibility to run the tests (in parallel) on systems with existing hardware TPMs. The implementation is adapted from tpm2-tss-engine (https://github.com/tpm2-software/tpm2-tss-engine/pull/107, sh_log_compiler.sh).

Closes #7.

[codecov[bot]]

Codecov Report

Merging #18 into master will decrease coverage by 3.8%. The diff coverage is 65.8%.

@@            Coverage Diff             @@
##           master      #18      +/-   ##
==========================================
- Coverage   84.34%   80.53%   -3.81%     
==========================================
  Files           3        4       +1     
  Lines         658      745      +87     
==========================================
+ Hits          555      600      +45     
- Misses        103      145      +42

Impacted Files	Coverage Δ
src/libtpm2-totp.c	84.66% <100%> (ø)	:arrow_up:
src/tpm2-totp-tcti.c	52.23% <52.23%> (ø)
src/tpm2-totp.c	81.06% <68.18%> (-1.59%)	:arrow_down:
test/libtpm2-totp.c	81.25% <79.41%> (-8.23%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 8dba9e8...bde2981. Read the comment docs.

[diabonas]

Awesome, tss2-tctildr will indeed make things much easier :+1: