## Problem
A customer reported that their Lambda is behind a proxy, and the
Rust-based extension encounters an error when sending logs and metrics
to Datadog via the proxy.

A previous PR
#961 fixed this
for traces and stats, but not for other things because the customer and
I didn't see any error with them at that time.

## This PR

Applies the env var `DD_TLS_CERT_FILE` to logs flusher and proxy flusher
as well.
Example: `DD_TLS_CERT_FILE=/opt/ca-cert.pem`, so the when the extension
flushes logs or proxied data to Datadog, the HTTP client created can
load and use this cert, and connect the proxy properly.

## Testing
1. Create a Lambda in a VPC with a proxy EC2 instance.
2. Connect to the proxy instance. With the help of ChatGPT, set up a
custom-build nginx with `ngx_http_proxy_connect_module`
3. Save the CA certificate from the proxy server to local machine
4. In the CDK stack, add a layer to the Lambda, which includes the CA
certificate `ca-cert.pem`
5. Set env vars:
    - `DD_TLS_CERT_FILE=/opt/ca-cert.pem`
- `DD_PROXY_HTTPS=http://10.0.0.30:3128`, where `10.0.0.30` is the
private IP of the proxy EC2 instance
    - `DD_LOG_LEVEL=debug`
6. Invoke the Lambda

## Result
**Before:**
Log flushing failed:
> DD_EXTENSION | ERROR | LOGS | Failed to send request after 97 ms and 3
attempts: reqwest::Error { kind: Request, url:
"https://http-intake.logs.datadoghq.com/api/v2/logs", source:
hyper_util::client::legacy::Error(Connect, ConnectFailed(Custom { kind:
Other, error: Custom { kind: InvalidData, error:
InvalidCertificate(UnknownIssuer) } })) }

**After:**
No such error

## Next steps
Do the same thing for dogstatsd metric flusher. Metric flusher is in a
separate repo https://github.com/DataDog/serverless-components, so let's
create separate PRs for that change.

## Notes
Customer report issue:
#919

…er (#984)

## Motivation
A customer reported that their Lambda is behind a proxy, and the
Rust-based extension encounters an error when sending logs and metrics
to Datadog via the proxy.

## Overview

Previous PRs in fixed this for traces/stats
(#961) and
logs/proxy
(#979).
DataDog/serverless-components#61 in
`serverless-components` repo fixed this issue for dogstatsd metrics.
This PR upgrades the dependency on `serverless-components` to patch this
update.

## Testing 
#### Steps
See #979

#### Result
**Before:**
Metrics flushing failed:
> DD_EXTENSION | DEBUG | Flushing 0 series and 1 distributions
DD_EXTENSION | DEBUG | Sending distributions: SketchPayload { ... }
DD_EXTENSION | DEBUG | Request to
https://api.datadoghq.com/api/beta/sketches took 144ms
DD_EXTENSION | ERROR | Error shipping data: None Failed to send request
after 3 attempts
DD_EXTENSION | ERROR | Failed to flush some metrics due to shipping
errors: 0 series and 1 sketches

**After:**
Metrics flushing succeeded:
> DD_EXTENSION | DEBUG | Flushing 0 series and 1 distributions
DD_EXTENSION | DEBUG | Sending distributions: SketchPayload { ... }
DD_EXTENSION | DEBUG | Request to
https://api.datadoghq.com/api/beta/sketches took 619ms
DD_EXTENSION | DEBUG | Successfully flushed 0 series and 1 distributions

## Notes
Customer report issue:
#919

## Problem
A customer reported that their Lambda is behind a proxy, and the
Rust-based extension can't send traces to Datadog via the proxy, while
the previous go-based extension worked.

## This PR
Supports the env var `DD_TLS_CERT_FILE`: The path to a file of
concatenated CA certificates in PEM format.
Example: `DD_TLS_CERT_FILE=/opt/ca-cert.pem`, so the when the extension
flushes traces/stats to Datadog, the HTTP client created can load and
use this cert, and connect the proxy properly.

## Testing
### Steps
1. Create a Lambda in a VPC with an NGINX proxy.
2. Add a layer to the Lambda, which includes the CA certificate
`ca-cert.pem`
3. Set env vars:
    - `DD_TLS_CERT_FILE=/opt/ca-cert.pem`
- `DD_PROXY_HTTPS=http://10.0.0.30:3128`, where `10.0.0.30` is the
private IP of the proxy EC2 instance
    - `DD_LOG_LEVEL=debug`
4. Update routing rules of security groups so the Lambda can reach
`http://10.0.0.30:3128`
5. Invoke the Lambda
### Result
**Before**
Trace flush failed with error logs:
> DD_EXTENSION | ERROR | Max retries exceeded, returning request error
error=Network error: client error (Connect) attempts=1
DD_EXTENSION | ERROR | TRACES | Request failed: No requests sent

**After**
Trace flush is successful:
> DD_EXTENSION | DEBUG | TRACES | Flushing 1 traces
DD_EXTENSION | DEBUG | TRACES | Added root certificate from
/opt/ca-cert.pem
DD_EXTENSION | DEBUG | TRACES | Proxy connector created with proxy:
Some("http://10.0.0.30:3128")
DD_EXTENSION | DEBUG | Sending with retry
url=https://trace.agent.datadoghq.com/api/v0.2/traces payload_size=1120
max_retries=1
DD_EXTENSION | DEBUG | Received response status=202 Accepted attempt=1
DD_EXTENSION | DEBUG | Request succeeded status=202 Accepted attempts=1
DD_EXTENSION | DEBUG | TRACES | Flushing took 1609 ms

## Notes
This fix only covers trace flusher and stats flusher, which use
`ServerlessTraceFlusher::get_http_client()` to create the HTTP client.
It doesn't cover logs flusher and proxy flusher, which use a different
function (http.rs:get_client()) to create the HTTP client. However, logs
flushing was successful in my tests, even if no certificate was added.
We can come back to logs/proxy flusher if someone reports an error.