Fix --sanity-check-only for Bundle

[Flamefire]

(created using eb --new-pr)

Includes:

• Fix setting of component directories when using buildininstalldir #4065

When running only the sanity check we must avoid creating the fake module which may not be possible when skipping the other steps. E.g buildenv requires a set up toolchain.
So load the real module instead by using sanity_check_load_module

For simplicity I pulled it out from the components sanity check and set a flag if we require loading it as a test

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS buildenv-default-foss-2023b.eb

Build succeeded for 1 out of 1 (total: 2 secs) (1 easyconfigs in total)
i8036 - Linux Rocky Linux 9.6, x86_64, AMD EPYC 7352 24-Core Processor (zen2), 8 x NVIDIA NVIDIA A100-SXM4-40GB, 580.65.06, Python 3.9.21
See https://gist.github.com/Flamefire/0e4957b7cbe423838a85db6c9feb4b55 for a full test report.