…eSpan-returns-null.js to test the intended OTelTracer.startSpan case where the internal createSpan API returns a null

The change away from `NODE_VERSION` in #2627 surprisingly
broke running the benchmarks. `NODE_VERSION` is used by nvm
and exporting it (?) makes a difference?

…ue with github deps (#2696)

mysql2@2.2.3 (and only that version) has a github dep:
    "@types/mysql": "types/mysql",
Attempting to install that version with npm v6 (the npm in node v10, v12, and
v14) hits npm/cli#4896 which results in an
install so slow that is hits the default 2 minute 'npm install' timeout
in the `tav` tool.

This adds a 'links' option to `createTransaction` and `createSpan` APIs
for specifying span links.
    apm.startSpan('name', { links: [ ... ] })
https://github.com/elastic/apm/blob/main/specs/agents/span-links.md
Span links support is added to the OTel Bridge as well:
    tracer.startSpan('name', { links: [ ... ] })

This adds a `traceContinutationStrategy` configuration option to allow
some control over how the APM Agent uses incoming trace-context headers
for context propagation.
https://github.com/elastic/apm/blob/main/specs/agents/trace-continuation.md

This also fixes a whitespace parsing issue in TraceState.

Closes: #2592
Closes: #2673
Closes: #2554
Obsoletes: #2555

AFAIK the "compatible runtimes" flag on Lambda layers is just advisory.

Co-authored-by: apmmachine <infra-root-apmmachine@elastic.co>

This avoids the name collision with the "exitSpan" option when creating
a span in the public API.

Closes: #2680

The old 'hapi' package was itself deprecated about 2 years ago.  The APM
agent now deprecates instrumenting it. The instrumentation code remains,
but it is no longer tested and will be removed in the next major.

Note that '@hapi/hapi' is still supported, this is just about the old
package name and versions. Any versions starting with 17.9.0, 18.2.0,
19 and later are the newer '@hapi/hapi'.

Refs: #2691

Co-authored-by: apmmachine <infra-root-apmmachine@elastic.co>

Co-authored-by: Trent Mick <trent.mick@elastic.co>

Co-authored-by: Trent Mick <trent.mick@elastic.co>

Co-authored-by: Trent Mick <trent.mick@elastic.co>