opam - opam 2.1.3 release

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We are pleased to announce the minor release of opam 2.1.3.

This opam release consists of backported fixes:

Fix opam init and opam init --reinit when the jobs variable has been set in the opamrc or the current config. (#5056)
opam var no longer fails if no switch is set (#5025)
Setting a variable with option --switch <sw> fails instead of writing an invalid switch-config file (#5027)
Handle external dependencies when updating switch state pin status (all pins), instead as a post pin action (only when called with opam pin (#5046)
Remove windows double printing on commands and their output (#4940)
Stop Zypper from upgrading packages on updates on OpenSUSE (#4978)
Clearer error message if a command doesn't exist (#4112)
Actually allow multiple state caches to co-exist (#4554)
Fix some empty conflict explanations (#4373)
Fix an internal error on admin repository upgrade from OPAM 1.2 (#4965)

and improvements:

When inferring a 2.1+ switch invariant from 2.0 base packages, don't filter out pinned packages as that causes very wide invariants for pinned compiler packages (#4501)
Some optimisations to opam list --installable queries combined with other filters (#4311)
Improve performance of some opam list combinations (e.g. --available, --installable) (#4999)
Improve performance of opam list --conflicts-with when combined with other filters (#4999)
Improve performance of opam show by as much as 300% when the package to show is given explicitly or is unique (#4997)(#4172)
When a field is defined in switch and global scope, try to determine the scope also by checking switch selection (#5027)

You can also find API changes in the release note.

Opam installation instructions (unchanged):

From binaries: run
```
bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.1.3"
```
or download manually from the Github "Releases" page to your PATH. In this case, don't forget to run opam init --reinit -ni to enable sandboxing if you had version 2.0.0~rc manually installed or to update you sandbox script.
From source, using opam:
```
opam update; opam install opam-devel
```
(then copy the opam binary to your PATH as explained, and don't forget to run opam init --reinit -ni to enable sandboxing if you had version 2.0.0~rc manually installed or to update your sandbox script)
From source, manually: see the instructions in the README.

We hope you enjoy this new minor version, and remain open to bug reports and suggestions.