fix: use http.Error for sending errors

This sets a few headers that prevent browsers from misinterpreting the error
text.

core: call app.Stop once

explain what dhtclient does

release: v0.4.21-rc3

This time, we'll actually build it.

fix race between adding tags and registering services with the connection manager

Hopefully helps fix #6271 and a bunch of other related issues.

disable write coalescing

See: https://github.com/libp2p/go-libp2p/issues/644

release: go-ipfs 0.4.21-rc2

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doc: remove out of date documentation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>