remove yamux read buffer

The current version has some build issues.

Accidentally added in #6361. The yamux transport now disables this globally by
default.

dep: update yamux and bitswap

* yamux: reduce goroutines per connection from 3 to 2.
* bitswap:
  - fix a very slow memory leak
  - adds an option for disabling providing (unused for now)
  - fixes a race condition on start
  - tag peers with outstanding requests in the connection manager

dep: update go-libp2p

* Write coalescing in yamux and mplex.
* Correctly tag relay streams.
* Reset relay streams instead of closing them. Fixes #6237.
* Trim connections in a background task instead of on-connect.

ci: actually enable golangci-lint

commands/swarm(fix): handle empty multiaddrs

Forbids empty multiaddr, fixes #6354

release v0.4.21-rc1

Prepare for release.

feat: improve errors when a path fails to parse

fix vendoring dependencies when building the source tarball

core: Use correct default for connmgr lowWater

Most people weren't affected by this as those values are set in config at init, but for others it would be rather hard to debug.

TMPDIR is a special variable indicating the _system_ temporary directory root.
Unfortunately, go refuses to honor `go.mod` files in this directory to prevent
random `/tmp/go.mod` files from messing with modules cloned into `/tmp`.

The fix is simple: rename TMPDIR to TEMP.

This helps with issues like #4190 by telling the user the path that failed to
parse.

fixes #4190

doc: remove out of date documentation

Add generation of dependency changes to mkreleaselog

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>

readme: remove mention of DCO

Add golangci-lint

docs+mk: update guidance for unsupported platforms

fix formatting in object get

fail start when loading a plugin fails

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

License: MIT
Signed-off-by: Dominic Della Valle <ddvpublic@gmail.com>

The git plugin is built-in. Anyways, there's no reason plugin loading shouldn't
work in travis.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

Otherwise, we simply panic later.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

fixes #6337

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

fix a typo in the issue template