Crater for rustdoc test merging

Crater run for rust-lang#126245

[CRATER] Crater rollup

This is a crater rollup of:
* rust-lang#124141
* rust-lang#130285
* rust-lang#130367

**What is a crater rollup?** It's simply a (manually set-up) crater job that is run on all of the containing PRs together, and then we can set the crates list for each of these jobs to *just* the list of failures after it's done. It should cut out on the bulk of "normal" crates that do nothing and simply just waste time to build without being affected by the union of all of these changes.

After this is finished, I will adjust all of the jobs to use only the list of failed crates. That should significantly speed up these jobs from taking like ~6 days to taking ~2. See the last time I did this: rust-lang#129660.

Given that rust-lang#130285 is running in build-and-test mode, let's run all of them in build-and-test mode.

…es, r=<try>

Use environment variables instead of command line arguments for merged doctests

Fixes [rust-lang#130796](rust-lang#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang#130285)). I'll start a crater run once CI passed.

cc `@ehuss`
r? `@notriddle`

…es, r=<try>

Use environment variables instead of command line arguments for merged doctests

Fixes [rust-lang#130796](rust-lang#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang#130285)). I'll start a crater run once CI passed.

cc `@ehuss`
r? `@notriddle`

…bles, r=notriddle

Use environment variables instead of command line arguments for merged doctests

Fixes [rust-lang#130796](rust-lang#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang#130285)). I'll start a crater run once CI passed.

cc `@ehuss`
r? `@notriddle`

…bles, r=notriddle

Use environment variables instead of command line arguments for merged doctests

Fixes [rust-lang#130796](rust-lang#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang#130285)). I'll start a crater run once CI passed.

cc ``@ehuss``
r? ``@notriddle``

Rollup merge of rust-lang#131095 - GuillaumeGomez:switch-to-env-variables, r=notriddle

Use environment variables instead of command line arguments for merged doctests

Fixes [rust-lang#130796](rust-lang#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang#130285)). I'll start a crater run once CI passed.

cc ``@ehuss``
r? ``@notriddle``

…otriddle

Use environment variables instead of command line arguments for merged doctests

Fixes [#130796](rust-lang/rust#130796).

Before merging this one, let's first ensure it has a smaller impact compared to command line arguments (results can be seen [here](rust-lang/rust#130285)). I'll start a crater run once CI passed.

cc ``@ehuss``
r? ``@notriddle``