`TlsUtil.keyManager()` uses `TrustManagerFactory.getDefaultAlgorithm()` to initialize `KeyManagerFactory`

[lbarrios]

Describe the bug

In TlsUtil.keyManager(), the KeyManagerFactory is instantiated using the default algorithm of TrustManagerFactory instead of KeyManagerFactory:

opentelemetry-java/exporters/common/src/main/java/io/opentelemetry/exporter/internal/TlsUtil.java

Lines 86 to 87 in 250021c

	KeyManagerFactory kmf =
	KeyManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());

Why it matters

Depending on the JVM configuration, the default algorithm for TrustManagerFactory may not be a valid algorithm name for KeyManagerFactory, which would cause a NoSuchAlgorithmException.

Expected behavior

KeyManagerFactory kmf =
    KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());

[jkwatson]

Are you able to put in a PR to fix this? Thanks!