I noticed in https://github.com/matrix-org/synapse/issues/8575 that the `end_error` variable in `synapse_port_db` is set to an `Exception`, even though later we expect it to be a `str`.

This PR simply casts an exception raised to a string. I'm doing this instead of having `end_error` be of type exception as we explicitly set `end_error` to a str here:

https://github.com/matrix-org/synapse/blob/d25eb8f3709965d0face01a041d5292490bf0139/scripts/synapse_port_db#L542-L547

This whole file could probably use some heavy refactoring, but until then at least this fix will prevent exception contents from being hidden from us and users.

* Move schema file

* Add a .

* Add matching changelog entry

* Fix sqlite

We need to make sure we are readu for the `set_cache_factor` callback.

Signed-off-by: Vasilis Gerakaris <vasilis.gerakaris@navarino.gr>

* Add `DeferredCache.get_immediate` method

A bunch of things that are currently calling `DeferredCache.get` are only
really interested in the result if it's completed. We can optimise and simplify
this case.

* Remove unused 'default' parameter to DeferredCache.get()

* another get_immediate instance

By using the "poll" reactor since macOS doesn't support epoll.

This should reduce the number of `There was no active span` errors we
see.

Fixes #8510.

Most of these uses don't need a full-blown DeferredCache; LruCache is lighter and more appropriate.

Fix the Connection protocol according to typeshed's assertions about sqlite3.Connection

This seems to have been broken since #6513.

* type annotations for LruCache

* changelog

* Apply suggestions from code review

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

* review comments

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

rather than have everything that instantiates an LruCache manage metrics
separately, have LruCache do it itself.

EventBuilder.build wants auth events these days

Support modifying event content from ThirdPartyRules modules

This implements a more standard API for instantiating a homeserver and
moves some of the dependency injection into the test suite.

More concretely this stops using `setattr` on all `kwargs` passed to `HomeServer`.

Optionally sends typing, presence, and read receipt information to appservices.

This PR makes several changes to the `./scripts-dev/lint.sh` script, which lints the codebase with a number of tools:

* Adds usage information, with `-h` flag to show it. Otherwise it will show when providing an unknown flag.
* Adds option `-d` which will check both staged and unstaged files that have changed since the last commit and add them to the list of files to lint.
  - Note that only files without an extension, or with a `.py` extension will be allowed. This prevents editing bash scripts causing the linters to break on non-python files.
* Improves the print-out of which files/directories are being linted. 

We asserted that the IDs returned by postgres sequence was greater than
any we had seen, however this is technically racey as we may update the
current positions out of order.

We now assert that the sequences are correct on startup, so the
assertion is no longer really required, so we remove them.

This seemed to entail dragging in a type stub for SortedList.

Rename Cache to DeferredCache, and related changes

Include user agent in user daily visits table.

Simplify `_locally_reject_invite`