small code formatting changes

+ use strip_heredoc to make the text in tests much more readable

`current_application_settings` used by `influx_metrics_enabled`
executed a markdown parsing code that was measured using `Gitlab::Metrics.measure`

But since the Gitlab::Metrics::InfluxDb was not yet build so Gitlab::Metrics
did not yet have `measure` method. Causing the NoMethodError.

However If run was successful at least once then result was cached in a file and this code never executed again.
Which caused this issue to only show up in CI preparation step.

 + rename controler method to #index from #metrics
 + remove assertion from nullMetric

+ Use NullMetrics to mock metrics when unused
+ Use method_missing in NullMetrics mocking
+ Update prometheus gem to version that correctly uses transitive dependencies
+ Ensure correct folders are used in Multiprocess prometheus client tests.
+ rename Sessions controller's metric

 + remove unecessarey require
 + fix small formatiing issues

+ Add spaces for four phases approach
+ fix InfluxDB rename

+ Cleanup Gemfile

Prometheus requires a trailing newline in its response.

+ cleanup

metrics wip

This is a step for #29118.

Add a single metric to count successful logins.

Summary types are not supported so remove Collector.  Either
we need to support the summary type or we need to create a
multiprocess-friendly Collector.

Add config to load prometheus and set up the Collector and the
Exporter.

Fix `Gemfile` as current prometheus-client gemspec is missing the
`mmap2` dependency.

Skip loading application settings from the database when migrations are pending

Closes gitlab-ee#2361

See merge request !11842

Style people in issuable search bar

Closes #30468

See merge request !11402

Use throttle when window is resized

Closes #33222

See merge request !11857

Refactor specs for WikiPage services

See merge request !11862

Resolve "Merge conflict resolution removed the newline in the end of file"

Closes #32983

See merge request !11817

Add translations for elapsed time in words

Closes #32747

See merge request !11769

Add optional path parameter and fix tests

Closes #33242

See merge request !11868

SystemCheck library for executing checks from a rake task

See merge request !9173

Fix hard-deleting users when they have authored issues

Closes #33215

See merge request !11855