Add lock around static ECC ecc_oid_cache

[cconlon]

Description

This PR adds a lock around the static ecc_oid_cache that is used by wc_ecc_get_oid() in wolfcrypt/src/ecc.c when HAVE_OID_ENCODING is defined.

Threading issues around this were showing up in wolfSSL JNI testing, with exceptions/errors similar to the following:

    [junit] JNI Ecc Class
    [junit] 	threadedEccSharedSecretTest
    [junit] com.wolfssl.wolfcrypt.WolfCryptException: ASN oid error, unknown sum id
    [junit] 	eccCurveSizeFromName
    [junit] 	at com.wolfssl.wolfcrypt.Ecc.wc_EccPrivateKeyDecode(Native Method)
    [junit] 	threadedEccSignVerifyTest
    [junit] 	at com.wolfssl.wolfcrypt.Ecc.privateKeyDecode(Unknown Source)
    [junit] 	at com.wolfssl.wolfcrypt.test.EccTest$3.run(EccTest.java:463)
    [junit] 	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
    [junit] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
    [junit] 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    [junit] 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    [junit] 	at java.base/java.lang.Thread.run(Thread.java:1583)

Testing

Tested via existing unit tests, and wolfSSL JNI threaded ECC tests which exposed this issue.

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[cconlon]

Retest this please Jenkins

[cconlon]

Retest this please Jenkins

[cconlon]

Retest this please Jenkins