docs: update configure examples

[Arnav-Purushotam-CUBoulder]

Autotools ./configure requires selecting a TLS backend explicitly (or using --without-ssl). Several docs/examples still show ./configure without any TLS backend flag, which fails on current sources.

Update example commands to include a representative TLS backend (--with-openssl) in:

• docs/INSTALL.md
• docs/tests/TEST-SUITE.md
• docs/ALTSVC.md
• docs/HTTPSRR.md
• GIT-INFO.md

Also note in docs/INSTALL.md that libpsl is enabled by default, and if libpsl is not available it can be disabled with --without-libpsl.

No functional code changes.

Checks:

• ./scripts/checksrc-all.pl

[vszakats]

When no TLS is selected, configure will say this, which I think is a reasonable
way to drive builders to select their TLS of choice:

configure: error: select TLS backend(s) or disable TLS with --without-ssl.

Select from these:

  --with-amissl
  --with-gnutls
  --with-mbedtls
  --with-openssl (also works for BoringSSL and LibreSSL)
  --with-rustls
  --with-schannel
  --with-wolfssl

Given the other TLS options, I'm not sure hard-wiring OpenSSL to all documentation is ideal,
where the context is TLS-backend agnostic.

[bagder]

I'm not sure hard-wiring OpenSSL to all documentation is ideal

I totally agree. A primary reason there is no default choice done is because we want to avoid "taking sides" or pick a winner. Pushing for OpenSSL in all documentation would be another way we would push for a specific backend.

The help text also says it all and a user should have few doubts about what the next step should be, and the choice is then up to the user and not proposed by us.

[bagder]

Thanks!